Patent Grant
9438622
1. Field of the Invention
The present invention relates generally to network security and more particularly to detecting malicious network content.
2. Related Art
Presently, malicious network content (e.g., malicious software or malware) can attack various devices via a communication network. For example, malware may include any program or file that is harmful to a computer user, such as bots, computer viruses, worms, Trojan horses, adware, spyware, or any programming that gathers information about a computer user or otherwise operates without permission.
Adware is a program configured to direct advertisements to a computer or a particular user. In one example, adware identifies the computer and/or the user to various websites visited by a browser on the computer. The website may then use the adware to either generate pop-up advertisements or otherwise direct specific advertisements to the user's browser. Spyware is a program configured to collect information regarding the user, the computer, and/or a user's network habits. In an example, spyware may collect information regarding the names and types of websites that the user browses and then transmit the information to another computer. Adware and spyware are often added to the user's computer after the user browses to a website that hosts the adware and/or spyware. The user is often unaware that these programs have been added and are similarly unaware of the adware and/or spyware's function.
Various processes and devices have been employed to prevent the problems that malicious network content can cause. For example, computers often include antivirus scanning software that scans a particular client device for viruses. Computers may also include spyware and/or adware scanning software. The scanning may be performed manually or based on a schedule specified by a user associated with the particular computer, a system administrator, and so forth. Unfortunately, by the time a virus or spyware is detected by the scanning software, some damage on the particular computer or loss of privacy may have already occurred.
In some instances, malicious network content comprises a bot. A bot is a software robot configured to remotely control all or a portion of a digital device (e.g., a computer) without authorization by the digital device's legitimate owner. Bot related activities include bot propagation and attacking other computers on a network. Bots commonly propagate by scanning nodes (e.g., computers or other digital devices) available on a network to search for a vulnerable target. When a vulnerable computer is scanned, the bot may install a copy of itself. Once installed, the new bot may continue to seek other computers on a network to infect. A bot may also be propagated by a malicious web site configured to exploit vulnerable computers that visit its web pages.
A bot may also, without the authority of the infected computer user, establish a command and control communication channel to receive instructions. Bots may receive command and control communication from a centralized bot server or another infected computer (e.g., via a peer-to-peer (P2P) network established by a bot on the infected computer). When a plurality of bots (i.e., a botnet) act together, the infected computers (i.e., zombies) can perform organized attacks against one or more computers on a network, or engage in criminal enterprises. In one example, bot infected computers may be directed to flood another computer on a network with excessive traffic in a denial-of-service attack. In another example, upon receiving instructions, one or more bots may direct the infected computer to transmit spam across a network. In a third example, bots may host illegal businesses such as pharmaceutical websites that sell pharmaceuticals without a prescription.
Malicious network content may be distributed over a network via web sites, e.g., servers operating on a network according to an HTTP standard. Malicious network content distributed in this manner may be actively downloaded and installed on a user's computer, without the approval or knowledge of the user, simply by accessing the web site hosting the malicious network content. The web site hosting the malicious network content may be referred to as a malicious web site. The malicious network content may be embedded within data associated with web pages hosted by the malicious web site. For example, a web page may include JavaScript code, and malicious network content may be embedded within the JavaScript code. In this example, the malicious network content embedded within the JavaScript code may be obfuscated such that it is not apparent until the JavaScript code is executed that the JavaScript code contains malicious network content. Therefore, the malicious network content may attack or infect a user's computer before detection by antivirus software, firewalls, intrusion detection systems, or the like.
Beginning on or about 2009, it became a widespread practice for the authors of bots to use malicious documents in the Portable Document Format (PDF) of Adobe Systems Inc. to propagate web borne attacks. Malicious PDF documents were hosted on web servers controlled by criminals, and then links to them created from many other websites. Innocent users could therefore accidentally, without realizing, browse a website which would cause a malicious PDF to be loaded into their browser, and from their into a PDF reader, which it would then exploit in order to gain control of the user's computer account, or entire computer. From there, malicious bot software would be installed.
According to some embodiments, the present invention may be directed to methods detecting malicious portable document format (PDF) network content may include at least the steps of (a) examining at least a portion of received PDF network content to determine if one or more suspicious characteristics indicative of malicious network content are included in the at least a portion of PDF network content; and (b) wherein if the at least a portion of PDF network content is determined to include one or more suspicious characteristics indicative of malicious network content, providing the at least a portion of PDF network content to one or more virtual machines to verify the inclusion of malicious network content in the at least a portion of PDF network content.
Network content may include any data transmitted over a network (i.e., network data). Network data may include text, software, images, audio, or other digital data. An example of network content includes web content, or any network data that may be transmitted using a Hypertext Transfer Protocol (HTTP), HyperText Markup Language (HTML) protocol, or be transmitted in a manner suitable for display on a web browser software application. Another examples of network content includes email messages, which may be transmitted using an email protocol such as Simple Mail Transfer Protocol (SMTP), Post Office Protocol version 3 (POP3), or Internet Message Access Protocol (IMAP4). A further example of network content includes Instant Messages, which may be transmitted using an Instant Messaging protocol such as Session Initiation Protocol (SIP) or Extensible Messaging and Presence Protocol (XMPP). In addition, network content may include any network data that is transferred using other data transfer protocols, such as File Transfer Protocol (FTP). We distinguish network content from network protocol header information used for addressing, routing, and otherwise delivering the network content.
To detect malicious network content (e.g., malicious web content) being transmitted over a communication network to a computing device, a virtual machine may be used to simulate the receipt and processing of network content on the receiving system. A determination may be made as to whether the network content is malicious based on a response of the virtual machine to the network content. Sometimes, suspicious network content is determined to be non-malicious. Processing the suspicious network content in a virtual machine is an important step to determine whether the suspicious network content is in fact malicious and prevent a false assumption that the suspicious network content is malicious. False positives in detecting malicious network content may be avoided by processing suspicious network content in a virtual machine and detecting malicious network content by analyzing the virtual machine's response to the suspicious network content.
In the prior art, a proxy may be used in the network between the computing device and a web server hosting the malicious network content. The proxy may intercept a request for network content issued by a web browser executing on the computing device. The proxy may then issue the request to the web server as a proxy on behalf of the computing device. The proxy may receive a response to the request from the web server. The proxy may then process a data exchange including the request and response on a virtual machine and evaluate the virtual machine's response to the data exchange to detect malicious network content. If no malicious network content is detected, the proxy may forward the requested network content to the computing device from which the original request originated.
Because each data exchange is processed using a virtual machine, this approach is highly computation intensive, and is not scalable for large numbers of computing devices on a network. Also, because the requested network content is not delivered to the computing device until after it has been determined that the requested network content does not include malicious network content, a significant delay is introduced between the request for network content and the delivery of the requested network content.
Provos et al. (N. Provos, P. Mavrommatis, M. A. Rajab, and F. Monrose, “All your iFRAMEs Point to Us,” Google Technical Report Provos-2008a, Feb. 4, 2008) reported on an analysis of web malware using a large web repository and corpus of malicious URLs. Provos et al. collected data for the analysis by first using a machine-learning framework in a pre-processing phase to extract features from web pages in the web repository and translate the features into a likelihood score. Next, a virtual machine was used in a verification phase to verify candidates identified by the machine-learning framework. Approximately 0.1% of the web pages in the web repository were processed by the virtual machine in the verification phase. Provos et al. noted that exhaustive inspection of each URL in the repository is prohibitively expensive. The system used by Provos et al. relied on a crawler proceeding gradually through the web to gather data in the repository for inspection, and could not inspect and select web pages in transit in the network for examination in a virtual machine.
The communication network 120 may include a public computer network such as the Internet, or a private computer network such as a wireless telecommunication network, wide area network, or local area network, or a combination of networks. Though the communication network 120 may include any type of network and be used to communicate different types of data, communications of web data may be discussed below for purposes of example.
The server device 105 and the client device 110 may include digital devices. Some examples of digital devices include computers, servers, laptops, personal digital assistants, and cellular telephones. The server device 105 may be configured to transmit network data over the communication network 120 to the client device 110. The client device 110 may be configured to receive the network data from the server device 105. The network data may include network content, such as web pages transmitted using a network communications protocol (e.g., Hypertext Transfer Protocol, or HTTP). In various embodiments, the server device 105 may include a web server configured to provide network content. The client device 110 may include a web browser configured to retrieve and/or display network content.
The tap 115 may include a digital data tap configured to monitor network data and provide a copy of the network data to the malicious network content detection system 125. Network data may comprise signals and data that are transmitted over the communication network 120 including data flows from the server device 105 to the client device 110. In one example, the tap 115 monitors and copies the network data without an appreciable decline in performance of the server device 105, the client device 110, or the communication network 120. The tap 115 may copy any portion of the network data. For example, the tap 115 may receive and copy any number of data packets from the network data.
In some embodiments, the network data may be organized into one or more data flows and provided to the malicious network content detection system 125. In various embodiments, the tap 115 may sample the network data based on a sampling scheme. Data flows may then be reconstructed based on the network data samples.
The tap 115 may also capture metadata from the network data. The metadata may be associated with the server device 105 and/or the client device 110. For example, the metadata may identify the server device 105 and/or the client device 110. In some embodiments, the server device 105 transmits metadata, which is captured by the tap 115. In other embodiments, a heuristic module 130 (described herein) may determine the server device 105 and the client device 110 by analyzing data packets within the network data in order to generate the metadata.
The malicious network content detection system 125 may include a digital device, software, or a combination thereof that receives network data from the tap 115. The malicious network content detection system 125 includes a heuristic module 130, a heuristics database 135, a scheduler 140, a virtual machine pool 145, and an analysis environment 150. In some embodiments, the tap 115 may be contained within the malicious network content detection system 125.
The heuristic module 130 receives the copy of the network data from the tap 115 and applies heuristics to the data to determine if the network data might contain suspicious network content. The heuristics applied by the heuristic module 130 may be based on data and/or rules stored in the heuristics database 135. In one example, the heuristic module 130 flags network data as suspicious after applying a heuristic analysis. The network data may then be buffered and organized into a data flow. The data flow may then be provided to the scheduler 140. In some embodiments, the suspicious network data is provided directly to the scheduler 140 without buffering or organizing the data flow. In other embodiments, a notification of a group of data flows (e.g., a set of related web page requests and responses) may be sent to the scheduler 140 for later retrieval by the virtual machine.
The heuristic module 130 may perform one or more heuristic analyses on the network data. The heuristic module 130 may retain data packets belonging to a particular data flow previously copied by the tap 115. In one example, the heuristic module 130 receives data packets from the tap 115 and stores the data packets within a buffer or other memory. Once the heuristic module 130 receives a predetermined number of data packets from a particular data flow, the heuristic module 130 performs the heuristics and/or probability analysis.
In some embodiments, the heuristic module 130 performs a heuristic analysis on a set of data packets belonging to a data flow and then stores the data packets within a buffer or other memory. The heuristic module 130 may then continue to receive new data packets belonging to the same data flow. Once a predetermined number of new data packets belonging to the same data flow are received, the heuristic analysis may be performed upon the combination of buffered and new data packets to determine a likelihood of suspicious network content.
In some embodiments, an optional buffer receives the flagged network data from the heuristic module 130. The buffer may be used to store and organize the flagged network data into one or more data flows before providing the one or more data flows to the scheduler 140. In various embodiments, the buffer is used to store network data until the network data is provided to the scheduler 140. In one example, the buffer stores the network data to allow other components of the malicious network content detection system 125 time to complete functions or otherwise clear data congestion.
In some embodiments, the heuristic module 130 may maintain copies of network content data of potential interest to virtual machines and provide the network content data on request (e.g., when a web browser later executes inside a virtual machine and requests entities that were transmitted on the network earlier). The length of time that the heuristic module 130 keeps this data in memory may be based on how suspicious the data is, how much workload the system is under, and/or other factors.
The scheduler 140 may identify the client device 110 and retrieve a virtual machine associated with the client device 110. A virtual machine is software that is configured to mimic the performance of a device (e.g., the client device 110). The virtual machine may be retrieved from the virtual machine pool 145. Furthermore, the scheduler 140 may identify a web browser running on the client device 110, and retrieve a virtual machine associated with the web browser.
In some embodiments, the heuristic module 130 transmits the metadata identifying the client device 110 to the scheduler 140. In other embodiments, the scheduler 140 receives one or more data packets of the network data from the heuristic module 130 and analyzes the one or more data packets to identify the client device 110. In yet other embodiments, the metadata may be received from the tap 115.
The scheduler 140 may retrieve and configure the virtual machine to mimic the pertinent performance characteristics of the client device 110. In one example, the scheduler 140 configures the characteristics of the virtual machine to mimic only those features of the client device 110 that are affected by the network data copied by the tap 115. The scheduler 140 may determine the features of the client device 110 that are affected by the network data by receiving and analyzing the network data from the tap 115. Such features of the client device 110 may include ports that are to receive the network data, select device drivers that are to respond to the network data, and any other devices coupled to or contained within the client device 110 that can respond to the network data. In other embodiments, the heuristic module 130 may determine the features of the client device 110 that are affected by the network data by receiving and analyzing the network data from the tap 115. The heuristic module 130 may then transmit the features of the client device to the scheduler 140.
The virtual machine pool 145 may be configured to store one or more virtual machines. The virtual machine pool 145 may include software and/or a storage medium capable of storing software. In one example, the virtual machine pool 145 stores a single virtual machine that can be configured by the scheduler 140 to mimic the performance of any client device 110 on the communication network 120. The virtual machine pool 145 may store any number of distinct virtual machines that can be configured to simulate the performance of a wide variety of client devices 110.
The analysis environment 150 simulates the receipt and/or display of the network content from the server device 105 after the network content is received by the client device 110 to analyze the effects of the network content upon the client device 110. The analysis environment 150 may identify the effects of malware or malicious network content by analyzing the simulation of the effects of the network content upon the client device 110 that is carried out on the virtual machine. There may be multiple analysis environments 150 to simulate multiple streams of network content. The analysis environment 150 is further discussed with respect to
Although
The virtual switch 210 may include software that is capable of forwarding packets of flagged network content to the virtual machine 215. In one example, the replayer 205 simulates the transmission of the data flow by the server device 105. The virtual switch 210 simulates the communication network 120, and the virtual machine 215 simulates the client device 110. The virtual switch 210 may route the data packets of the data flow to the correct ports of the virtual machine 215.
In some embodiments, requests for data from client software in the virtual machine 215 (e.g., a web browser) may be proxied by the replayer to the heuristic module 130 where the data has been cached, and a response from the heuristic module 130 may then be proxied back to the client software executing in the virtual machine 215.
The virtual machine 215 includes a representation of the client device 110 that may be provided to the analysis environment 150 by the scheduler 140. In one example, the scheduler 140 retrieves an instance of the virtual machine 215 from the virtual machine pool 145 and configures the virtual machine 215 to mimic a client device 110. The configured virtual machine 215 is then provided to the analysis environment 150 where it may receive flagged network content from the virtual switch 210.
As the analysis environment 150 simulates the transmission and reception of the network content, behavior of the virtual machine 215 can be closely monitored for unauthorized activity. If the virtual machine 215 crashes, performs illegal operations, performs abnormally, or allows access of data to an unauthorized entity (e.g., an unauthorized computer user, a bot, etc.), the analysis environment 150 may react. In one example, the analysis environment 150 may transmit a command to the client device 110 to stop accepting the network content or data flows from the server device 105.
In some embodiments, the analysis environment 150 monitors and analyzes the behavior of the virtual machine 215 in order to determine a specific type of malware or malicious network content. The analysis environment 150 may also generate computer code configured to eliminate new viruses, worms, bots, adware, spyware, or other malware or malicious network content. In various embodiments, the analysis environment 150 generates computer code configured to repair damage performed by malware or malicious network content. By simulating the transmission and reception of suspicious network content and analyzing the response of the virtual machine 215, the analysis environment 150 may identify known and previously unidentified malware and malicious network content before a computer system is damaged or compromised.
In step 310, a packet of network content is inspected. The heuristic module 130 may utilize one or more heuristics to inspect the packet of network content for suspicious network content which indicates the potential presence of malicious network content or malware within the packet.
A packet of network content may be part of a data flow which includes additional packets of network content. For example, the packet of network content may represent a portion of a web page, while other related packets in the data flow represent additional portions of the web page. The packet of network content may be stored along with the other related packets of network content comprising the data flow, such that multiple packets of network content within the data flow may be inspected in a sequence or in parallel. The malicious network content detection system may store the packets of network content and all or a portion of a data flow. The data flow and data packets may be stored for any length of time, from a few seconds to minutes, tens of minutes, or more, for analysis at any time.
To facilitate longer storage times for data flows over a high data rate communication network, large data objects comprised of numerous data packets may be truncated to a small subset of representative data packets. Data object truncation is particularly useful where network communication bandwidth is mostly utilized by a small percentage of large data objects, such as video. For example, video data may be truncated to a few data packets, such as the first few data packets. An extent to which the large data objects are truncated may be adaptive based on available memory, data bandwidth, type of data objects, and other factors. An amount of memory allocated to storing a data flow may also be dependent upon a characteristic of the data flow, such as data type. In an example, octet streams, text streams, HTML streams, and miscellaneous binary streams may be allocated 1 megabyte (MB). Images and PDF files may be allocated 384 kilobytes (kB). Video, audio, and most other data types may be allocated 128 kB. The memory allocated to storing each data flow type may be adjusted, periodically or dynamically, to improve analysis throughput while maintaining accuracy in detection of malicious network content and working within memory limitations.
In step 315, a suspicious characteristic of the network content is identified. The heuristic module 130 may identify the suspicious characteristic of the network content as a result of inspecting the network content in step 310. When a characteristic of the packet, such as a sequence of characters or keyword, is identified that meets the conditions of a heuristic used in step 310, a suspicious characteristic or “feature” of the network content is identified. The identified features may be stored for reference and analysis. In some embodiments, the entire packet may be inspected and multiple features may be identified before proceeding to the next step. In some embodiments, features may be determined as a result of an analysis across multiple packets comprising the network content.
Keywords used by heuristics may be chosen by performing an approximate Bayesian probability analysis of all the keywords in an HTML specification using a corpus of malicious network content and a corpus of non-malicious network content. The approximate Bayesian probability analysis may be based on the principles of the Bayesian theorem and/or naïve Bayesian classification. For instance, a probability Pm that the keyword appears in malicious network content may be computed using the corpus of malicious network content, while a probability Pn that the keyword appears in non-malicious network content may be computed using the corpus of non-malicious network content. A given keyword may be determined to be a suspicious characteristic for being associated with malicious network content if a score based on a computed ratio Pm/Pn exceeds a threshold of suspicion. The threshold of suspicion may be a value greater than 1, 10, 30, 60, 100, or some other number indicating how much more likely the suspicious characteristic is to indicate malicious network content than to indicate non-malicious network content.
In step 320, a score related to a probability that the suspicious characteristic identified in step 315 indicates malicious network content is determined. An approximate Bayesian probability analysis may be used to determine the score. In various embodiments, the approximate Bayesian probability analysis may be performed in real-time or using a look-up table based on a previously performed approximate Bayesian probability analysis.
For example, the approximate Bayesian probability analysis may be performed to determine a relative probability score that a particular feature is associated with the presence of malicious network content in a packet by comparing a corpus of malicious network content and a corpus of regular, non-malicious network content. A feature may include a characteristic of the packet, such as a sequence of characters or keyword, that meets the conditions of a heuristic used in step 310. The feature may also include a characteristic involving more than one packet inspected in sequence or in parallel. An example of a feature may include the character sequence “eval(unescape(”, which indicates a JavaScript “unescape” command nested within a JavaScript “eval” command argument. Further examples of features are described below with respect to step 445 in method 400. A probability Pf|m that the feature is present in a packet of malicious network content is computed by analyzing the corpus of malicious network content. A probability Pf|n that the feature is present in a packet of non-malicious network content is computed by analyzing the corpus of non-malicious network content. A malicious probability score is computed as the base two logarithm of a relative probability factor Pm|f that the feature is associated with malicious network content. The malicious probability score is computed by computing the ratio of the base two logarithm (log2) of the probability that the feature is present in a packet of malicious network content and the base two logarithm of the probability that the feature is present in a packet of non-malicious network content. The relative probability factor Pm|f may be expressed as follows:
log2(Pm|f)=log2(Pf|m)/log2(Pf|n) Equation 1
The size of the result log2(Pm|f) (i.e., malicious probability score) may indicate the probability that the suspicious network content includes malicious network content. For example, a result of eleven may indicate that the feature is approximately two thousand times more likely to appear in malicious network content than in non-malicious network content. Likewise, a value of twelve may indicate that the feature is approximately four thousand times more likely to appear in malicious network content.
In some embodiments, the malicious corpus and/or the non-malicious corpus may be continuously updated in response to monitored network data traffic, and the malicious probability scores associated with the features may be continuously updated in response to the updates to the corpuses. In other embodiments, the corpuses may be created and used in advance to store pre-computed malicious probability scores in a look-up table for reference when features are identified. The features associated with significant probabilities of malicious network content may change as the corpuses change.
In step 325, malicious network content is identified or flagged if the malicious probability score of a feature computed in step 320 satisfies an analysis threshold. The analysis threshold may be greater than 1, 10, 30, 60, 100, 1000, 2000, or higher. The analysis threshold may be preset, or may be variable based on operating conditions of the malicious network content detection system 125. If the malicious probability score does not satisfy the analysis threshold, no action may be taken with regard to the feature associated with the malicious probability score. Otherwise, the analysis may proceed to the next step, such as step 330 for analysis through processing by a virtual machine, such as the virtual machine 215. In some embodiments, the malicious probability scores of all features computed in step 320 may be compared against the analysis threshold to assign a priority level to each feature and/or the packet as a whole. The priority level may be computed based on a variety of factors, such as the number of features identified in the packet, the highest malicious probability score of a feature in the packet, an average malicious probability score of the features in the packet, a mean malicious probability score of the features in the packet, and the like.
The analysis threshold may be adaptive or be frequently updated based on operating conditions of the malicious network content detection system 125. For example, the threshold value may be dynamically revised according to a quantity of packets of network content to be inspected. As a quantity of data packets which are intercepted and/or copied from the network data transmission in step 310 increases, a quantity of data packets to be inspected may also increase. This may increase a computational load and leave less computational bandwidth available for more detailed analysis of the data packets. Consequently, the threshold may be increased to compensate for the decrease in available computational bandwidth for more detailed analysis. As another example, the threshold value may be dynamically revised according to an availability of one or more virtual machines to be used for the more detailed analysis. The threshold value may be set such that only features which have a significant probability of indicating malicious network content are processed using a virtual machine. For example, out of over one thousand features, less than fifty may be considered significant.
There may be multiple dynamically adaptive thresholds, which may be synchronized with each other. For example, the scheduler 140 may use a threshold to determine whether a virtual machine should be dispatched to process a queued suspicious network content. The scheduler 140's threshold may increase due to lack of available computational resources for the analysis environment 150 to execute virtual machines. The heuristic module 130 may use another threshold to determine whether heuristics should be applied to an identified feature. The heuristic module 130's threshold may be based on the malicious probability score for the identified feature. As the scheduler 140's threshold increases, the heuristic module 130's threshold may also increase. This is because flagging suspicious network content based on running heuristics on identified features may be irrelevant and an inefficient use of computational resources if the scheduler 140 will not process the suspicious network content in a virtual machine due to an increased threshold in the scheduler 140.
After suspicious network content has been flagged at step 325 for further analysis, the entire stored data flow including the suspicious network content may be reanalyzed. Each feature may be given a higher malicious probability score by virtue that one feature in the data flow has been found to have a malicious probability score greater than the threshold. A priority level for each feature found in the data flow may also be increased. Furthermore, all data packets and data flows associated with any domains associated with suspicious network content may be cached and given higher priorities and malicious probability scores than they would otherwise. The scheduler 140 may execute the virtual machine to process each flagged suspicious network content in the data flow individually, in priority order, in their original sequence of presentation, or in some other order. The virtual machine may process the suspicious network content until pre-empted by a higher priority suspicious network content.
In step 330, a virtual machine is executed to process the suspicious network content. The virtual machine may effectively replay the suspicious network content in a web browser executing on the virtual machine. The heuristic module 130 may provide the packet containing the suspicious network content to the scheduler 140, along with a list of the features present in the packet and the malicious probability scores associated with each of those features. Alternatively, the heuristic module 130 may provide a pointer to the packet containing the suspicious network content to the scheduler 140 such that the scheduler 140 may access the packet via a memory shared with the heuristic module 130. In another embodiment, the heuristic module 130 may provide identification information regarding the packet to the scheduler 140 such that the scheduler 140, replayer 205, or virtual machine may query the heuristic module 130 for data regarding the packet as needed.
The heuristic module 130 may also provide a priority level for the packet and/or the features present in the packet. The scheduler 140 may then load and configure a virtual machine from the virtual machine pool 145, and dispatch the virtual machine to the analysis environment 150 to process the suspicious network content. The virtual machine may be configured to execute for a minimum amount of processing, or for a minimum period of time, such as approximately 45 seconds. After the minimum period of time passes, the virtual machine may be pre-empted by the scheduler 140 to dispatch another virtual machine. Multiple virtual machines may be run simultaneously.
The scheduler 140 may choose which feature to process first according to the priority levels provided by the heuristic module 130. The scheduler 140 may cause another virtual machine already processing or analyzing another feature or packet, or set of packets, in the analysis environment 150 to terminate prior to dispatching the loaded virtual machine. For example, this may occur if computational resources are occupied with other virtual machines processing other features and therefore are not available to execute the loaded virtual machine. The scheduler 140 may choose which virtual machine(s) to terminate based on the priority levels of the features being processed by the virtual machine, how much time the virtual machine has already spent executing, or other reasons.
The scheduler 140 may reprioritize suspicious network content already in queue to be processed by virtual machines based on newly identified suspicious network content. For example, already queued suspicious network content may be reprioritized if there is a domain identified in common with the newly identified suspicious network content. Numerous incidents of suspicious network content associated with a single domain may increase the priority of all suspicious network content associated with the domain.
The replayer 205 in the analysis environment 150 may keep track of network content requested by the virtual machine. If suspicious network content already in the scheduler 140's queue is requested and processed by the virtual machine while processing other previously dispatched suspicious network content, and the queued suspicious network content is not found to be malicious, then the scheduler 140 may delete the queued suspicious network content from the queue. In this way, computational requirements can be reduced because an item of suspicious network content may only be processed in a virtual machine once, rather than each time a reference to the item of suspicious network content is made by another item of suspicious network content.
In step 335, malicious network content is detected by analyzing the virtual machine response to the suspicious network content. The analysis environment 150 may be configured to monitor the virtual machine for indications that the suspicious network content is in fact malicious network content. The analysis environment 150 may monitor the virtual machine for unusual memory accesses, unusual spawning of executable processes, unusual network transmissions, crashes, unusual changes in performance, and the like. The analysis environment may flag the suspicious network content as malicious network content according to the observed behavior of the virtual machine.
If a virtual machine processes suspicious network content for greater than a predetermined amount of time without any malicious network content being detected, the scheduler 140 may terminate the virtual machine to free up computational resources. The predetermined amount of time may be variable, according to a queue of suspicious network content that is awaiting processing by a virtual machine, the probability that the suspicious network content may be malicious network content, the feature being evaluated by the virtual machine, available computational resources, and the like. For example, the predetermined amount of time may be 45 seconds, two minutes, twenty minutes, or any other length of time.
If the suspicious network content is determined to be malicious network content, the malicious network content detection system 125 may report the malicious network content and/or log the malicious network content for future reference. For example, the malicious network content detection system 125 may generate an alert for a network content packet detected to include malicious network content. The malicious network content detection system 125 may report the malicious network content to an entity responsible for the client device 105. If the malicious network content was determined to originate from the server device 105, the client device 110 may be instructed not to continue network transmissions with the server device 105. If a party responsible for the server device 105 is known, the malicious network content detection system 125 may report the malicious network content to the party responsible for the server device 105. The server device 105 may be added to a list of malicious network content providers, and future network transmissions originating from the server device 105 may be blocked from reaching their intended destinations.
In step 405, a data character is read from the data packet. The data character read may be subsequent to the character sequence “HTTP” or a data character previously read in a prior iteration of step 405. A pointer may be incremented to indicate the next data character to read in the method 400.
In step 410, the data character read in step 405 is evaluated to determine if the data character may indicate the start of a possible keyword or a possible feature as described with respect to method 300, or a different kind of data (e.g., JavaScript content embedded in HTML content). The data character may include a left angled bracket (i.e., “<”), for example. If the data character read may indicate the start of a keyword or a feature, the method may proceed to step 415. Otherwise, the method may proceed to step 420.
In step 415, a new state is pushed onto the stack of states to indicate that the method 400 has encountered the start of a keyword or feature. The new state may be an InKeyword state to indicate that the method is in the midst of processing a keyword. Depending on the character read, a different new state may be pushed onto the stack. A string of data characters may be stored, starting with the most recent character read or the next character to be read. The method 400 then proceeds to step 440.
In step 420, the data character read in step 405 is evaluated to determine if the data character may indicate the end of a keyword or a feature as described with respect to method 300. The data character may include a right angled bracket (i.e., “>”), for example. If the data character read may indicate the end of a keyword or a feature, the method may proceed to step 425. Otherwise, the method may proceed to step 440.
In step 425, heuristics to be applied to the data packet are identified and applied based on a character string read, which may start with the data character identified in step 410 and end with the data character identified in step 420. The heuristic module 300 may store the character string. The character string may be compared against a database of character strings stored in the heuristics database 135 to determine one or more heuristics that may be applied to the data packet based on the keyword. In some embodiments, a list of results of applying heuristics may be created. The list of results may be stored so that the list may be referenced in step 445.
Some examples of a heuristic that may be applied to the packet include keyword matches. Some keywords may be associated more with malicious network content than non-malicious network content, and their presence in a packet of network content may be an indication that the packet contains suspicious network content.
In one exemplary heuristic, an object filename's extension following a period may be examined. For example, a filename ending in the characters “.ini”, “.anr”, or “.htm” may be determined to be suspicious. Also, a filename generally associated with one filetype but associated with a different file type in the reference may be determined to be suspicious. For example, a filename ending in “.jpg” which is not referring to an image file may be determined to be suspicious.
In other exemplary heuristics, content of web pages may be analyzed to determine whether network content is suspicious. For example, presence of small iframes, such as an iframe in which the width and/or height is 0 or 1 pixel, in a web page may be determined to be suspicious.
Further examples of heuristics may be associated with JavaScript code sequences. When an “eval(unescape( . . . ))” JavaScript command sequence, which includes an “unescape” command nested within the argument of an “eval” command, is detected in the data packet, the heuristic may evaluate the command sequence to identify suspicious network content. The “eval(unescape( . . . ))” command sequence may be used to obfuscate malicious network content so that the malicious network content is not easily detected in the network data transmission, and may therefore indicate suspicious network content.
Another example of a heuristic is a length of the argument of the “unescape” or other JavaScript function from a starting character to an ending character. The length may be determined by counting a number of characters, or measuring a length of time, between the opening parenthesis and the closing parenthesis after “unescape” or other function name. A greater number of characters between the parentheses may indicate that an obfuscated body to the command is being used.
Bi-gram detection is another exemplary heuristic that may be employed in JavaScript or other types of network content. In bi-gram detection, character transitions within the network content are analyzed. A table of conditional probabilities may be generated and updated continuously as data is evaluated. The table of conditional probabilities indicates the probability of each second character appearing after each first character. The conditional probability of a second character C2 given the first character C1 may be written as P(C2|C1). The heuristic may identify when a string of unusual character transitions occurs according to the table of conditional probabilities. Thresholds for the length of the string of unusual character transitions, combined with the values of the conditional probabilities that flags the character transitions as being unusual, may be set a priori based on an approximate Bayesian probability analysis using a corpus of malicious network content and a corpus of non-malicious network content. Alternatively, the thresholds may be adjusted in near real time as the table of conditional probabilities is updated. For example, a long string of unusual character transitions may indicate the presence of malicious network content in a JavaScript “eval(unescape( . . . ))” clause.
The use of domain profiles is another exemplary heuristic that may be used to reduce a rate of false positives from other heuristics. The domain profiles heuristic may be used in conjunction with other heuristics in order to increase throughput and reduce computational requirements for detecting malicious network content. Each network domain with which monitored network content is exchanged may be cataloged and annotated with a list of the features present in network content associated with the network domain. A typical network domain may be approximately constant in the features present in associated network content. When a feature is identified by another heuristic, the feature may be looked up in the list of features associated with the network domain. If the feature is listed as being associated with the network domain, and malicious network content was not previously detected due to identification of the feature in network content associated with the domain, a virtual machine may not be executed to process the network content containing the feature associated with the network domain. If, on the other hand, the feature was not previously detected or associated with the network domain, the network content may be identified as being suspicious and processed by a virtual machine.
A list of domains or web sites containing malicious network content may be maintained. The list of sources of malicious network content may be hosted on the computer network and accessible by clients on the computer network. The heuristic module 130 may access the list of domains and web sites containing malicious network content to supplement the information provided by the domain profiles heuristic. For example, the threshold for network content associated with a web site on a list of malicious network content sources may be set to be lower and/or the priority of a suspicious network content may be set higher than for other network content. When malicious network content is detected, the list of domains may be notified or updated with the information for reference by others.
In step 430, if a state is being exited, the state being exited is popped from the stack of states. The state being exited is the most recent state pushed onto the stack of states. For example, if the state being exited is the InKeyword state, the InKeyword state is popped from the stack of states to indicate that the method is no longer in the midst of reading a keyword. If a state is not being exited, a state may not be popped from the stack, and multiple states may be stored on the stack. In some embodiments, up to 32 states may be present on the stack of states at one time. For example, JavaScript may have embedded HTML, and therefore multiple states may be active at one time to account for nested features. In various embodiments, there may be more than 60 states associated with data packets being analyzed for malicious network content.
In step 435, a new state is pushed onto the stack of states to indicate that the method is now in the midst of a new state. The new state may be determined by the last keyword that was read, or a character indicating a new kind of content. For example, the new state may be an InBetweenKeyword state to indicate that the method is awaiting another keyword to process. In some embodiments, the new state may be an InJavaScript state to indicate that the method is in the midst of reading a JavaScript segment. The state may impact which heuristics are identified and applied to the packet of web data in step 445. For example, a first heuristic may be chosen if a first state is active, whereas a second heuristic may be chosen if a second state is active.
In step 440, the count of characters read in step 405 is evaluated to determine if the data character may lie at the end of a packet. If the data character lies at the end of the packet, the method may proceed to step 445. Otherwise, the method may proceed to step 405.
In step 445, the list of results produced by applying the heuristics in step 425 for the features in the data packet are referenced to determine which features in the data packet are to be processed using a virtual machine. Malicious probability scores for each feature may be compared against a threshold to determine whether the feature indicates suspicious network content. The features associated with the data packet may be ranked in priority order. The features may be used to prioritize whether to refer the data packet, and associated content, to a virtual machine in the order identified in step 425, in the priority order determined by their respective malicious probability scores, or in some other order.
The communications network interface 525 may communicate with other digital devices (not shown) via the communications medium 540. The processor 505 executes instructions. The memory system 510 permanently or temporarily stores data. Some examples of the memory system 510 are RAM and ROM. The storage system 515 also permanently or temporarily stores data. Some examples of the storage system 515 are hard disks and disk drives. The I/O interface 530 may include any device that can receive input and provide output to a user. The I/O interface 530 may include, but is not limited to, a keyboard, a mouse, a touchscreen, a keypad, a biosensor, a compact disc (CD) drive, a digital versatile disc (DVD) drive, or a floppy disk drive. The display interface 535 may include an interface configured to support a display, monitor, or screen. In some embodiments, the controller 500 comprises a graphical user interface to be displayed to a user over a monitor in order to allow the user to control the controller 500.
According to other embodiments, malicious network content may also include malicious portable document format (PDF) network content. It will be understood that the term “malicious PDF network content” may be understood to include portable document format (PDF) files located on one or more server devices 105 and made available for distribution via the communication network 120 to one or more client devices 110.
Generally speaking, the tap 115 may be adapted to intercept requests to obtain PDF network content received from a web browser, PDF reader application, or any other application, module, or engine requesting such PDF network content, associated with a client device 110. In some embodiments, the tap 115 may be disposed between one or more client devices 110 and one or more server devices 105 and direct requests to obtain PDF network content into the malicious network content detection system 600, which will be described in greater detail infra with reference to
As background, PDF network content, such as a PDF document may include a fixed-layout document, that when parsed by a PDF reader application (not shown), produce a visual representation of the data included in the PDF document. The data within a PDF document is arranged in a hierarchical manner beginning with a header, a body portion that includes information indicative of one or more objects, a cross-reference table, also known as an “XREF” table, and a trailer. The header includes information indicative of the PDF specification version number to which the document adheres. The version number may be utilized to determine the PDF document reader version that is best adapted to parse the PDF document.
The XREF table includes offset information indicative of the position of objects within the PDF document. As such, the XREF table allows the PDF reader application to parse or walk individual portions (e.g., pages) of the PDF document without a need to parse or walk the entire PDF document. Lastly, the trailer of the PDF document allows the PDF reader application to efficiently locate the XREF table along with any other pertinent objects that may be utilized by the PDF reader application to construct the visual representation.
The body may contain one or more objects that comprise the contents of the PDF document. Generally speaking, the objects of a PDF document may include, but are not limited to, Boolean operators, numbers, names, strings, arrays, dictionaries, streams, and combinations thereof. The body may also include transparent objects such as metadata, security features, and the like.
Objects of a PDF document may be broadly categorized as either direct or indirect. It will be understood that direct objects may not reference other objects. Conversely, indirect object may make reference to one or more objects, which may include both direct and/or indirect objects. The PDF document may also include interactive elements such as AcroForm elements and XML Forms Data Format (XFDF elements). Both AcroForm and XFDF elements allow the inclusion of JavaScript code, also known as JavaScript API.
It will be understood that malware may be adapted to utilize JavaScript code to exploit vulnerabilities present within both PDF reader applications and web browser applications. It will further be understood that PDF reader applications and web browser applications may cooperate with one another via a plug-in. For example, when a web browser requests a PDF document, the PDF reader application is automatically launched to parse the PDF document. If the PDF document includes one or more objects that reference JavaScript code, the JavaScript codes called during parsing may construct virtual operating systems within the web browser for performing one or more functions associated with the JavaScript code.
While plug-in cooperation between the PDF reader application and web browser application provides significant benefits such as cross-platform compatibility (i.e., agnostic to the operating system of the client device 110), numerous vulnerabilities may be created within the web browser, which may expose the client device 110 to different types of malware, viruses, and the like.
In some embodiments, JavaScript code may exploit one or more vulnerabilities of the web browser application by loading memory allocated for operation of the PDF reader application with malicious code, often commonly referred to as “heap spray.” The heap spray may be adapted to prepare the memory allocated for the PDF reader application with shellcode. Once prepared, the vulnerable JavaScript code is called to trigger the vulnerability, execute the shellcode, and ultimately deliver a payload. It will be understood that the term “payload” may include any deleterious effect caused by malicious network content to the client device 110. It is noteworthy that the deleterious effects caused by malicious network content are far too numerous to include individually, but would be readily appreciated by one of ordinary skill in the art with the present disclosure before them. Non-limiting examples of deleterious effects include consumption of memory, overwriting or corruption of system or program files, and the like.
As with HTML documents, suspicious characteristics indicative of malicious network content included with a PDF document may be determined by way of the heuristic module 130 as previously described supra with reference to
Referring now to
The malicious network content detection system 600 may be adapted to determine suspicious characteristics indicative of malicious network content by way of methods disclosed with regard to HTML files, such as the exemplary method 400 for detecting malicious network content described above with regard to
Additionally, the PDF parser 605 may be adapted to determine one or more suspicious characteristics indicative of malicious network content that are unique to PDF network content. For example, the PDF parser 605 may be adapted to examine the body of PDF network content to located objects that include specific types of JavaScript code. Some non-limiting examples of JavaScript code that are commonly utilized to exploit vulnerabilities in web browser applications include eval( ), util.printf( ), and media.newPlayer( ).
Moreover, creators of PDF network content malware may attempt to obfuscate JavaScript code references to malware by splitting the JavaScript code into a plurality of objects that when referenced by the PDF reader application may be combined to execute the malicious code. Therefore, the PDF parser 605 may be adapted to determine obfuscated malicious JavaScript code divided across multiple objects utilizing the getField( ) function.
In additional embodiments, the PDF parser 605 may be adapted to determine malicious JavaScript code that is encrypted in to PDF network content utilizing software stream ciphers such as RC4 and AES encryption.
While the above examples contemplate the adaptability of the PDF parser 605 to determine suspicious content such as JavaScript code, the PDF parser 605 may be adapted to determine additional types of malware associated with other objects including, but not limited to, embedded Flash stream objects. For example, a Flash file may include ActionScript virtual machine instructions that are adapted to set up a heap spray with shellcode. In an additional example, malicious code may be incorporated into the PDF network content via one or more Tagged Image File Format (TIFF) vulnerabilities. It will be understood that some TIFF vulnerabilities may not utilize heap spray functionalities.
While not an exclusive list, the following features may be indicative of PDF network content having malicious network content: PDFBadVersion (determines if the PDF specification version number associated with the PDF network content is correct), PDFHeader1_0 (examines the header information of the PDF network document for errors, also known as malformed header information), PDFNameJS (examines the PDF document for PDF objects that include names incorporating JS that are indicative of JavaScript code), PDFNameJavaScript (examines the PDF document for PDF objects that include names incorporating JavaScript that are indicative of JavaScript code), PDFBadFileStart (examines the PDF network content for an improper file start signature), PDFNameOpenAction (examines the PDF network content for PDF objects that cause Javascript functionality to be run on the initial loading of the PDF content), PDFCouldNotParse (determines if the PDF parser is unable to properly parse the PDF network content), and/or combinations thereof. The PDF parser 605 may utilize the aforementioned features to determine one or more suspicious characteristics included in the PDF network content.
It will be understood that because one or more portions (e.g., pages) of PDF network content may be assembled without need to walk or parse the entire PDF network content, the PDF parser 605 may be adapted to evaluate only the portion(s) of the PDF network content that has been requested by the client device 110.
Regardless of the type or amount of suspicious characteristics located by the PDF parser 605, if one or more suspicious characteristics are determined to be included in at least a portion of the PDF network content, the at least a portion of PDF network content may be provided to one or more virtual machines for verification of malicious network content.
The one or more virtual machines may be selected from the virtual machine pool 145 based, in part, upon the particular PDF specification version number included in the header of the PDF network content being analyzed. In some embodiments, the one or more virtual machines may each include one or more augmented finite state machines. Each of these augmented finite state machines may include different configurations of computer readable instructions such as operating system instructions, web browser instructions, PDF reader application instructions, plug-in instructions for operatively coupling one or more web browsers to a PDF reader application, along with any additional types of computer readable instructions adapted to verify the inclusion of malicious network content in PDF network content.
In some embodiments, the use of a plurality (i.e., two or more) of augmented finite state machines may allows for PDF network content to be processed across various system configurations (i.e., permutations of operating system instructions, web browser instructions, and PDF reader application instructions). As such, PDF network content that may not exploit vulnerabilities within one type of web browser application may be verified to exploit vulnerabilities within additional types of web browser applications. These types of multi-faceted analyses are more likely to verify the presence of malicious network content within PDF network content that exploit vulnerabilities of specific versions of programs and/or applications.
Each of the augmented finite state machines includes an analysis environment 150 to simulate the receipt, compiling, execution, and/or display of the PDF network content from the server device 105 to analyze the effects of the PDF network content upon the client device 110. For example, the analysis environment 150 may include a web browser requesting the PDF network content from a server device 105. The web browser causes the PDF reader application to parse the PDF network content. If the PDF network content does, in fact, include malicious code (e.g., JavaScript, Flash, etc.), one or more of the vulnerabilities of the web browser application or the PDF reader application may be exploited by the malicious code to deliver a payload. The effects of the payload may be directly or indirectly observed within the analysis environment 150.
It will be understood that an exemplary analysis environment 150 is described supra in greater detail with reference to
In some embodiments, the malicious network content detection system 600 may be further adapted to index PDF network content verified to include malicious network content by associating the PDF network content with an identifier indicative of one or more domains from which the PDF network content was obtained and storing the associated PDF network content as a record that resides with one or more databases operatively coupled to one or more server devices 105.
The database may be utilized by the malicious network content detection system 600 to compare PDF network content determined to include one or more suspicious characteristics to the index of PDF network content previously verified to include malicious network. Additionally, all PDF network documents residing on domains determined to have hosted PDF network content verified to include malicious network content may be automatically reviewed without further examination of the PDF network content for suspicious characteristics.
Referring now to
Next, the method 700 may include the step 710 of examining the at least a portion of PDF network content to determine if one or more suspicious features and/or characteristics indicative of malicious network content are included in the at least a portion of PDF network content. As stated previously, examining may include utilizing heuristics or a PDF parser to determine the presence of specific features and/or specific vulnerable JavaScript code included with the at least a portion of PDF network content.
The method 700 may also include the step 715 of providing the at least a portion of PDF network content to one or more virtual machines (also known as augmented finite state machines).
Next, the inclusion of malicious network content in the at least a portion of PDF network content may be verified by executing or compiling the at least a portion of PDF network content in the one or more virtual machines in step 720. The compiling of the at least a portion of PDF network content causes vulnerable JavaScript code to execute any malicious network content associated therewith.
The method 700 then may include the step 725 of observing the performance of the one or more virtual machines to determine if the at least a portion of PDF network content, in fact, includes malicious network content. Observations of performance indicative of the execution of malicious network content include, but are not limited to the generation of heap spray within the memory allocated to the PDF reader application, the execution of shellcode, consumption of memory, overwriting or corruption of system or program files, and the like.
Lastly, the method 730 may include the step of preventing the delivery of the at least a portion of PDF network content verified to include malicious network to the client device from which the request was received.
The embodiments discussed herein are illustrative. As these embodiments are described with reference to illustrations, various modifications or adaptations of the methods and/or specific structures described may become apparent to those skilled in the art.
The above-described modules may be comprised of instructions that are stored on storage media (e.g., computer readable media). The instructions may be retrieved and executed by a processor (e.g., the processor 505). Some examples of instructions include software, program code, and firmware. Some examples of storage media comprise memory devices and integrated circuits. The instructions are operational when executed by the processor to direct the processor to operate in accordance with embodiments of the present invention. Those skilled in the art are familiar with instructions, processor(s), and storage media.
In the foregoing specification, the invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the invention is not limited thereto. Various features and aspects of the above-described invention can be used individually or jointly. Further, the invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art.
This application is a continuation of U.S. patent application Ser. No. 13/011,344 filed on Jan. 21, 2011, which is a continuation-in-part of U.S. patent application Ser. No. 12/263,971 entitled “Systems and Methods for Detecting Malicious Network Content” and filed on Nov. 3, 2008. This application is also related to co-pending U.S. patent application Ser. No. 11/409,355 entitled “Heuristic Based Capture with Replay to Virtual Machine” and filed on Apr. 20, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 11/152,286 entitled “Computer Worm Defense System and Method” and filed on Jun. 13, 2005, which claims the priority benefit of U.S. Provisional Patent Application Ser. No. 60/579,910 entitled “Computer Worm Defense System and Method” and filed on Jun. 14, 2004. U.S. patent application Ser. No. 11/409,355 is also a continuation-in-part of U.S. patent application Ser. No. 11/096,287 entitled “System and Method of Detecting Computer Worms” and filed on Mar. 31, 2005, which claims the priority benefit of U.S. Provisional Patent Application Ser. No. 60/559,198 entitled “System and Method of Detecting Computer Worms” and filed on Apr. 1, 2004. U.S. patent application Ser. No. 11/409,355 is also a continuation-in-part of U.S. patent application Ser. No. 11/151,812 entitled “System and Method of Containing Computer Worms” and filed on Jun. 13, 2005, which claims the priority benefit of U.S. Provisional Patent Application No. 60/579,953 entitled “System and Method of Containing Computer Worms” and filed on Jun. 14, 2004. Each of the aforementioned patent applications are incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4292580 | Ott et al. | Sep 1981 | A |
| 5175732 | Hendel et al. | Dec 1992 | A |
| 5440723 | Arnold et al. | Aug 1995 | A |
| 5490249 | Miller | Feb 1996 | A |
| 5537540 | Miller et al. | Jul 1996 | A |
| 5603027 | Ohkami | Feb 1997 | A |
| 5657473 | Killean et al. | Aug 1997 | A |
| 5842002 | Schnurer et al. | Nov 1998 | A |
| 5978917 | Chi | Nov 1999 | A |
| 6088803 | Tso et al. | Jul 2000 | A |
| 6094677 | Capek et al. | Jul 2000 | A |
| 6108799 | Boulay et al. | Aug 2000 | A |
| 6118382 | Hibbs et al. | Sep 2000 | A |
| 6269330 | Cidon et al. | Jul 2001 | B1 |
| 6272641 | Ji | Aug 2001 | B1 |
| 6279113 | Vaidya | Aug 2001 | B1 |
| 6298445 | Shostack et al. | Oct 2001 | B1 |
| 6357008 | Nachenberg | Mar 2002 | B1 |
| 6417774 | Hibbs et al. | Jul 2002 | B1 |
| 6424627 | S.o slashed.rhaug et al. | Jul 2002 | B1 |
| 6442696 | Wray et al. | Aug 2002 | B1 |
| 6484315 | Ziese | Nov 2002 | B1 |
| 6487666 | Shanklin et al. | Nov 2002 | B1 |
| 6493756 | O'Brien et al. | Dec 2002 | B1 |
| 6550012 | Villa et al. | Apr 2003 | B1 |
| 6700497 | Hibbs et al. | Mar 2004 | B2 |
| 6775657 | Baker | Aug 2004 | B1 |
| 6831893 | Ben Nun et al. | Dec 2004 | B1 |
| 6832367 | Choi et al. | Dec 2004 | B1 |
| 6895550 | Kanchirayappa et al. | May 2005 | B2 |
| 6898632 | Gordy et al. | May 2005 | B2 |
| 6907396 | Muttik et al. | Jun 2005 | B1 |
| 6941348 | Petry et al. | Sep 2005 | B2 |
| 6971097 | Wallman | Nov 2005 | B1 |
| 6981279 | Arnold et al. | Dec 2005 | B1 |
| 6995665 | Appelt et al. | Feb 2006 | B2 |
| 7007107 | Ivchenko et al. | Feb 2006 | B1 |
| 7028179 | Anderson et al. | Apr 2006 | B2 |
| 7043757 | Hoefelmeyer et al. | May 2006 | B2 |
| 7069316 | Gryaznov | Jun 2006 | B1 |
| 7080407 | Zhao et al. | Jul 2006 | B1 |
| 7080408 | Pak et al. | Jul 2006 | B1 |
| 7093002 | Wolff et al. | Aug 2006 | B2 |
| 7093239 | van der Made | Aug 2006 | B1 |
| 7096498 | Judge | Aug 2006 | B2 |
| 7100201 | Izatt | Aug 2006 | B2 |
| 7107617 | Hursey et al. | Sep 2006 | B2 |
| 7159149 | Spiegel et al. | Jan 2007 | B2 |
| 7213260 | Judge | May 2007 | B2 |
| 7231667 | Jordan | Jun 2007 | B2 |
| 7240364 | Branscomb et al. | Jul 2007 | B1 |
| 7240368 | Roesch et al. | Jul 2007 | B1 |
| 7243371 | Kasper et al. | Jul 2007 | B1 |
| 7249175 | Donaldson | Jul 2007 | B1 |
| 7251215 | Turner et al. | Jul 2007 | B1 |
| 7287278 | Liang | Oct 2007 | B2 |
| 7308716 | Danford et al. | Dec 2007 | B2 |
| 7328453 | Merkle, Jr. et al. | Feb 2008 | B2 |
| 7346486 | Ivancic et al. | Mar 2008 | B2 |
| 7356736 | Natvig | Apr 2008 | B2 |
| 7386888 | Liang et al. | Jun 2008 | B2 |
| 7392542 | Bucher | Jun 2008 | B2 |
| 7418729 | Szor | Aug 2008 | B2 |
| 7428300 | Drew et al. | Sep 2008 | B1 |
| 7441272 | Durham et al. | Oct 2008 | B2 |
| 7448084 | Apap et al. | Nov 2008 | B1 |
| 7458098 | Judge et al. | Nov 2008 | B2 |
| 7464404 | Carpenter et al. | Dec 2008 | B2 |
| 7464407 | Nakae et al. | Dec 2008 | B2 |
| 7467408 | O'Toole, Jr. | Dec 2008 | B1 |
| 7478428 | Thomlinson | Jan 2009 | B1 |
| 7480773 | Reed | Jan 2009 | B1 |
| 7487543 | Arnold et al. | Feb 2009 | B2 |
| 7496960 | Chen et al. | Feb 2009 | B1 |
| 7496961 | Zimmer et al. | Feb 2009 | B2 |
| 7516488 | Kienzle et al. | Apr 2009 | B1 |
| 7519990 | Xie | Apr 2009 | B1 |
| 7523493 | Liang et al. | Apr 2009 | B2 |
| 7530104 | Thrower et al. | May 2009 | B1 |
| 7540025 | Tzadikario | May 2009 | B2 |
| 7546638 | Anderson et al. | Jun 2009 | B2 |
| 7565550 | Liang et al. | Jul 2009 | B2 |
| 7568233 | Szor et al. | Jul 2009 | B1 |
| 7584455 | Ball | Sep 2009 | B2 |
| 7603715 | Costa et al. | Oct 2009 | B2 |
| 7607171 | Marsden et al. | Oct 2009 | B1 |
| 7639714 | Stolfo et al. | Dec 2009 | B2 |
| 7644441 | Schmid et al. | Jan 2010 | B2 |
| 7657419 | van der Made | Feb 2010 | B2 |
| 7676841 | Sobchuk et al. | Mar 2010 | B2 |
| 7698548 | Shelest et al. | Apr 2010 | B2 |
| 7707633 | Danford et al. | Apr 2010 | B2 |
| 7712136 | Sprosts et al. | May 2010 | B2 |
| 7730011 | Deninger et al. | Jun 2010 | B1 |
| 7739740 | Nachenberg et al. | Jun 2010 | B1 |
| 7779463 | Stolfo et al. | Aug 2010 | B2 |
| 7784097 | Stolfo et al. | Aug 2010 | B1 |
| 7832008 | Kraemer | Nov 2010 | B1 |
| 7836502 | Zhao et al. | Nov 2010 | B1 |
| 7849506 | Dansey et al. | Dec 2010 | B1 |
| 7854007 | Sprosts et al. | Dec 2010 | B2 |
| 7869073 | Oshima | Jan 2011 | B2 |
| 7877803 | Enstone et al. | Jan 2011 | B2 |
| 7904959 | Sidiroglou et al. | Mar 2011 | B2 |
| 7908660 | Bahl | Mar 2011 | B2 |
| 7930738 | Petersen | Apr 2011 | B1 |
| 7937761 | Bennett | May 2011 | B1 |
| 7949849 | Lowe et al. | May 2011 | B2 |
| 7996556 | Raghavan et al. | Aug 2011 | B2 |
| 7996836 | McCorkendale et al. | Aug 2011 | B1 |
| 7996904 | Chiueh et al. | Aug 2011 | B1 |
| 7996905 | Arnold et al. | Aug 2011 | B2 |
| 8006305 | Aziz | Aug 2011 | B2 |
| 8010667 | Zhang et al. | Aug 2011 | B2 |
| 8020206 | Hubbard et al. | Sep 2011 | B2 |
| 8028338 | Schneider et al. | Sep 2011 | B1 |
| 8042184 | Batenin | Oct 2011 | B1 |
| 8045094 | Teragawa | Oct 2011 | B2 |
| 8045458 | Alperovitch et al. | Oct 2011 | B2 |
| 8069484 | McMillan et al. | Nov 2011 | B2 |
| 8087086 | Lai et al. | Dec 2011 | B1 |
| 8171553 | Aziz et al. | May 2012 | B2 |
| 8176049 | Deninger et al. | May 2012 | B2 |
| 8176480 | Spertus | May 2012 | B1 |
| 8201246 | Wu et al. | Jun 2012 | B1 |
| 8204984 | Aziz et al. | Jun 2012 | B1 |
| 8214905 | Doukhvalov et al. | Jul 2012 | B1 |
| 8220055 | Kennedy | Jul 2012 | B1 |
| 8225288 | Miller et al. | Jul 2012 | B2 |
| 8225373 | Kraemer | Jul 2012 | B2 |
| 8233882 | Rogel | Jul 2012 | B2 |
| 8234640 | Fitzgerald et al. | Jul 2012 | B1 |
| 8234709 | Viljoen et al. | Jul 2012 | B2 |
| 8239944 | Nachenberg et al. | Aug 2012 | B1 |
| 8260914 | Ranjan | Sep 2012 | B1 |
| 8266091 | Gubin et al. | Sep 2012 | B1 |
| 8286251 | Eker et al. | Oct 2012 | B2 |
| 8291499 | Aziz et al. | Oct 2012 | B2 |
| 8307435 | Mann et al. | Nov 2012 | B1 |
| 8307443 | Wang et al. | Nov 2012 | B2 |
| 8312545 | Tuvell et al. | Nov 2012 | B2 |
| 8321936 | Green et al. | Nov 2012 | B1 |
| 8321941 | Tuvell et al. | Nov 2012 | B2 |
| 8332571 | Edwards, Sr. | Dec 2012 | B1 |
| 8365286 | Poston | Jan 2013 | B2 |
| 8365297 | Parshin et al. | Jan 2013 | B1 |
| 8370938 | Daswani et al. | Feb 2013 | B1 |
| 8370939 | Zaitsev et al. | Feb 2013 | B2 |
| 8375444 | Aziz et al. | Feb 2013 | B2 |
| 8381299 | Stolfo et al. | Feb 2013 | B2 |
| 8402529 | Green et al. | Mar 2013 | B1 |
| 8464340 | Ahn et al. | Jun 2013 | B2 |
| 8479174 | Chiriac | Jul 2013 | B2 |
| 8479276 | Vaystikh et al. | Jul 2013 | B1 |
| 8479291 | Bodke | Jul 2013 | B1 |
| 8510827 | Leake et al. | Aug 2013 | B1 |
| 8510828 | Guo et al. | Aug 2013 | B1 |
| 8510842 | Amit et al. | Aug 2013 | B2 |
| 8516478 | Edwards et al. | Aug 2013 | B1 |
| 8516590 | Ranadive et al. | Aug 2013 | B1 |
| 8516593 | Aziz | Aug 2013 | B2 |
| 8522348 | Chen et al. | Aug 2013 | B2 |
| 8528086 | Aziz | Sep 2013 | B1 |
| 8533824 | Hutton et al. | Sep 2013 | B2 |
| 8539582 | Aziz et al. | Sep 2013 | B1 |
| 8549638 | Aziz | Oct 2013 | B2 |
| 8555391 | Demir et al. | Oct 2013 | B1 |
| 8561177 | Aziz et al. | Oct 2013 | B1 |
| 8566946 | Aziz et al. | Oct 2013 | B1 |
| 8584094 | Dadhia et al. | Nov 2013 | B2 |
| 8584234 | Sobel et al. | Nov 2013 | B1 |
| 8584239 | Aziz et al. | Nov 2013 | B2 |
| 8595834 | Xie et al. | Nov 2013 | B2 |
| 8627476 | Satish et al. | Jan 2014 | B1 |
| 8635696 | Aziz | Jan 2014 | B1 |
| 8682054 | Xue et al. | Mar 2014 | B2 |
| 8682812 | Ranjan | Mar 2014 | B1 |
| 8689333 | Aziz | Apr 2014 | B2 |
| 8695096 | Zhang | Apr 2014 | B1 |
| 8713631 | Pavlyushchik | Apr 2014 | B1 |
| 8713681 | Silberman et al. | Apr 2014 | B2 |
| 8726392 | McCorkendale et al. | May 2014 | B1 |
| 8739280 | Chess et al. | May 2014 | B2 |
| 8776229 | Aziz | Jul 2014 | B1 |
| 8782792 | Bodke | Jul 2014 | B1 |
| 8789172 | Stolfo et al. | Jul 2014 | B2 |
| 8789178 | Kejriwal et al. | Jul 2014 | B2 |
| 8793787 | Ismael et al. | Jul 2014 | B2 |
| 8805947 | Kuzkin et al. | Aug 2014 | B1 |
| 8806647 | Daswani et al. | Aug 2014 | B1 |
| 8832829 | Manni et al. | Sep 2014 | B2 |
| 8850570 | Ramzan | Sep 2014 | B1 |
| 8850571 | Staniford et al. | Sep 2014 | B2 |
| 8881234 | Narasimhan et al. | Nov 2014 | B2 |
| 8881282 | Aziz et al. | Nov 2014 | B1 |
| 8898788 | Aziz et al. | Nov 2014 | B1 |
| 8935779 | Manni et al. | Jan 2015 | B2 |
| 8984638 | Aziz et al. | Mar 2015 | B1 |
| 8990939 | Staniford et al. | Mar 2015 | B2 |
| 8990944 | Singh et al. | Mar 2015 | B1 |
| 8997219 | Staniford et al. | Mar 2015 | B2 |
| 9009822 | Ismael et al. | Apr 2015 | B1 |
| 9009823 | Ismael et al. | Apr 2015 | B1 |
| 9027135 | Aziz | May 2015 | B1 |
| 9071638 | Aziz et al. | Jun 2015 | B1 |
| 9104867 | Thioux et al. | Aug 2015 | B1 |
| 9106694 | Aziz et al. | Aug 2015 | B2 |
| 9118715 | Staniford et al. | Aug 2015 | B2 |
| 20010005889 | Albrecht | Jun 2001 | A1 |
| 20010047326 | Broadbent et al. | Nov 2001 | A1 |
| 20020018903 | Kokubo et al. | Feb 2002 | A1 |
| 20020038430 | Edwards et al. | Mar 2002 | A1 |
| 20020091819 | Melchione et al. | Jul 2002 | A1 |
| 20020095607 | Lin-Hendel | Jul 2002 | A1 |
| 20020116627 | Tarbotton et al. | Aug 2002 | A1 |
| 20020144156 | Copeland | Oct 2002 | A1 |
| 20020162015 | Tang | Oct 2002 | A1 |
| 20020166063 | Lachman et al. | Nov 2002 | A1 |
| 20020169952 | DiSanto et al. | Nov 2002 | A1 |
| 20020184528 | Shevenell et al. | Dec 2002 | A1 |
| 20020188887 | Largman et al. | Dec 2002 | A1 |
| 20020194490 | Halperin et al. | Dec 2002 | A1 |
| 20030021728 | Sharpe et al. | Jan 2003 | A1 |
| 20030074578 | Ford et al. | Apr 2003 | A1 |
| 20030084318 | Schertz | May 2003 | A1 |
| 20030101381 | Mateev et al. | May 2003 | A1 |
| 20030115483 | Liang | Jun 2003 | A1 |
| 20030188190 | Aaron et al. | Oct 2003 | A1 |
| 20030191957 | Hypponen et al. | Oct 2003 | A1 |
| 20030200460 | Morota et al. | Oct 2003 | A1 |
| 20030212902 | van der Made | Nov 2003 | A1 |
| 20030229801 | Kouznetsov et al. | Dec 2003 | A1 |
| 20030237000 | Denton et al. | Dec 2003 | A1 |
| 20040003323 | Bennett et al. | Jan 2004 | A1 |
| 20040006473 | Mills et al. | Jan 2004 | A1 |
| 20040015712 | Szor | Jan 2004 | A1 |
| 20040019832 | Arnold et al. | Jan 2004 | A1 |
| 20040047356 | Bauer | Mar 2004 | A1 |
| 20040083408 | Spiegel et al. | Apr 2004 | A1 |
| 20040088581 | Brawn et al. | May 2004 | A1 |
| 20040093513 | Cantrell et al. | May 2004 | A1 |
| 20040111531 | Staniford et al. | Jun 2004 | A1 |
| 20040117478 | Triulzi et al. | Jun 2004 | A1 |
| 20040117624 | Brandt et al. | Jun 2004 | A1 |
| 20040128355 | Chao et al. | Jul 2004 | A1 |
| 20040165588 | Pandya | Aug 2004 | A1 |
| 20040236963 | Danford et al. | Nov 2004 | A1 |
| 20040243349 | Greifeneder et al. | Dec 2004 | A1 |
| 20040249911 | Alkhatib et al. | Dec 2004 | A1 |
| 20040255161 | Cavanaugh | Dec 2004 | A1 |
| 20040268147 | Wiederin et al. | Dec 2004 | A1 |
| 20050005159 | Oliphant | Jan 2005 | A1 |
| 20050021740 | Bar et al. | Jan 2005 | A1 |
| 20050033960 | Vialen et al. | Feb 2005 | A1 |
| 20050033989 | Poletto et al. | Feb 2005 | A1 |
| 20050050148 | Mohammadioun et al. | Mar 2005 | A1 |
| 20050086523 | Zimmer et al. | Apr 2005 | A1 |
| 20050091513 | Mitomo et al. | Apr 2005 | A1 |
| 20050091533 | Omote et al. | Apr 2005 | A1 |
| 20050091652 | Ross et al. | Apr 2005 | A1 |
| 20050108562 | Khazan et al. | May 2005 | A1 |
| 20050114663 | Cornell et al. | May 2005 | A1 |
| 20050125195 | Brendel | Jun 2005 | A1 |
| 20050149726 | Joshi et al. | Jul 2005 | A1 |
| 20050157662 | Bingham et al. | Jul 2005 | A1 |
| 20050183143 | Anderholm et al. | Aug 2005 | A1 |
| 20050201297 | Peikari | Sep 2005 | A1 |
| 20050210533 | Copeland et al. | Sep 2005 | A1 |
| 20050238005 | Chen et al. | Oct 2005 | A1 |
| 20050240781 | Gassoway | Oct 2005 | A1 |
| 20050262562 | Gassoway | Nov 2005 | A1 |
| 20050265331 | Stolfo | Dec 2005 | A1 |
| 20050283839 | Cowburn | Dec 2005 | A1 |
| 20060010495 | Cohen et al. | Jan 2006 | A1 |
| 20060015416 | Hoffman et al. | Jan 2006 | A1 |
| 20060015715 | Anderson | Jan 2006 | A1 |
| 20060015747 | Van de Ven | Jan 2006 | A1 |
| 20060021029 | Brickell et al. | Jan 2006 | A1 |
| 20060021054 | Costa et al. | Jan 2006 | A1 |
| 20060031476 | Mathes et al. | Feb 2006 | A1 |
| 20060047665 | Neil | Mar 2006 | A1 |
| 20060070130 | Costea et al. | Mar 2006 | A1 |
| 20060075496 | Carpenter et al. | Apr 2006 | A1 |
| 20060095968 | Portolani et al. | May 2006 | A1 |
| 20060101516 | Sudaharan et al. | May 2006 | A1 |
| 20060101517 | Banzhof et al. | May 2006 | A1 |
| 20060117385 | Mester et al. | Jun 2006 | A1 |
| 20060123477 | Raghavan et al. | Jun 2006 | A1 |
| 20060143709 | Brooks et al. | Jun 2006 | A1 |
| 20060150249 | Gassen et al. | Jul 2006 | A1 |
| 20060161983 | Cothrell et al. | Jul 2006 | A1 |
| 20060161987 | Levy-Yurista | Jul 2006 | A1 |
| 20060161989 | Reshef et al. | Jul 2006 | A1 |
| 20060164199 | Gilde et al. | Jul 2006 | A1 |
| 20060173992 | Weber et al. | Aug 2006 | A1 |
| 20060179147 | Tran et al. | Aug 2006 | A1 |
| 20060184632 | Marino et al. | Aug 2006 | A1 |
| 20060191010 | Benjamin | Aug 2006 | A1 |
| 20060221956 | Narayan et al. | Oct 2006 | A1 |
| 20060236393 | Kramer et al. | Oct 2006 | A1 |
| 20060242709 | Seinfeld et al. | Oct 2006 | A1 |
| 20060248519 | Jaeger et al. | Nov 2006 | A1 |
| 20060248582 | Panjwani et al. | Nov 2006 | A1 |
| 20060251104 | Koga | Nov 2006 | A1 |
| 20060288417 | Bookbinder et al. | Dec 2006 | A1 |
| 20070006288 | Mayfield et al. | Jan 2007 | A1 |
| 20070006313 | Porras et al. | Jan 2007 | A1 |
| 20070011174 | Takaragi et al. | Jan 2007 | A1 |
| 20070016951 | Piccard et al. | Jan 2007 | A1 |
| 20070033645 | Jones | Feb 2007 | A1 |
| 20070038943 | FitzGerald et al. | Feb 2007 | A1 |
| 20070064689 | Shin et al. | Mar 2007 | A1 |
| 20070074169 | Chess et al. | Mar 2007 | A1 |
| 20070094730 | Bhikkaji et al. | Apr 2007 | A1 |
| 20070101435 | Konanka et al. | May 2007 | A1 |
| 20070128855 | Cho et al. | Jun 2007 | A1 |
| 20070142030 | Sinha et al. | Jun 2007 | A1 |
| 20070143827 | Nicodemus et al. | Jun 2007 | A1 |
| 20070156895 | Vuong | Jul 2007 | A1 |
| 20070157180 | Tillmann et al. | Jul 2007 | A1 |
| 20070157306 | Elrod et al. | Jul 2007 | A1 |
| 20070168988 | Eisner et al. | Jul 2007 | A1 |
| 20070171824 | Ruello et al. | Jul 2007 | A1 |
| 20070174915 | Gribble et al. | Jul 2007 | A1 |
| 20070192500 | Lum | Aug 2007 | A1 |
| 20070192858 | Lum | Aug 2007 | A1 |
| 20070198275 | Malden et al. | Aug 2007 | A1 |
| 20070208822 | Wang et al. | Sep 2007 | A1 |
| 20070220607 | Sprosts et al. | Sep 2007 | A1 |
| 20070240218 | Tuvell et al. | Oct 2007 | A1 |
| 20070240219 | Tuvell et al. | Oct 2007 | A1 |
| 20070240220 | Tuvell et al. | Oct 2007 | A1 |
| 20070240222 | Tuvell et al. | Oct 2007 | A1 |
| 20070250930 | Aziz et al. | Oct 2007 | A1 |
| 20070256132 | Oliphant | Nov 2007 | A2 |
| 20070271446 | Nakamura | Nov 2007 | A1 |
| 20080005782 | Aziz | Jan 2008 | A1 |
| 20080018122 | Zierler et al. | Jan 2008 | A1 |
| 20080028463 | Dagon et al. | Jan 2008 | A1 |
| 20080032556 | Schreier | Feb 2008 | A1 |
| 20080040710 | Chiriac | Feb 2008 | A1 |
| 20080046781 | Childs et al. | Feb 2008 | A1 |
| 20080066179 | Liu | Mar 2008 | A1 |
| 20080072326 | Danford et al. | Mar 2008 | A1 |
| 20080077793 | Tan et al. | Mar 2008 | A1 |
| 20080080518 | Hoeflin et al. | Apr 2008 | A1 |
| 20080086720 | Lekel | Apr 2008 | A1 |
| 20080098476 | Syversen | Apr 2008 | A1 |
| 20080120722 | Sima et al. | May 2008 | A1 |
| 20080134178 | Fitzgerald et al. | Jun 2008 | A1 |
| 20080134334 | Kim et al. | Jun 2008 | A1 |
| 20080141376 | Clausen et al. | Jun 2008 | A1 |
| 20080184373 | Traut et al. | Jul 2008 | A1 |
| 20080189787 | Arnold et al. | Aug 2008 | A1 |
| 20080201778 | Guo et al. | Aug 2008 | A1 |
| 20080209557 | Herley et al. | Aug 2008 | A1 |
| 20080215742 | Goldszmidt et al. | Sep 2008 | A1 |
| 20080222728 | Chavez et al. | Sep 2008 | A1 |
| 20080222729 | Chen et al. | Sep 2008 | A1 |
| 20080263665 | Ma et al. | Oct 2008 | A1 |
| 20080295172 | Bohacek | Nov 2008 | A1 |
| 20080301810 | Lehane et al. | Dec 2008 | A1 |
| 20080307524 | Singh et al. | Dec 2008 | A1 |
| 20080313738 | Enderby | Dec 2008 | A1 |
| 20080320594 | Jiang | Dec 2008 | A1 |
| 20090003317 | Kasralikar et al. | Jan 2009 | A1 |
| 20090004427 | Sarrafi-Nour et al. | Jan 2009 | A1 |
| 20090007100 | Field et al. | Jan 2009 | A1 |
| 20090013408 | Schipka | Jan 2009 | A1 |
| 20090031423 | Liu et al. | Jan 2009 | A1 |
| 20090036111 | Danford et al. | Feb 2009 | A1 |
| 20090037835 | Goldman | Feb 2009 | A1 |
| 20090044024 | Oberheide et al. | Feb 2009 | A1 |
| 20090044274 | Budko et al. | Feb 2009 | A1 |
| 20090064332 | Porras et al. | Mar 2009 | A1 |
| 20090077666 | Chen et al. | Mar 2009 | A1 |
| 20090083369 | Marmor | Mar 2009 | A1 |
| 20090083855 | Apap et al. | Mar 2009 | A1 |
| 20090089879 | Wang et al. | Apr 2009 | A1 |
| 20090094697 | Provos et al. | Apr 2009 | A1 |
| 20090113425 | Ports et al. | Apr 2009 | A1 |
| 20090125976 | Wassermann et al. | May 2009 | A1 |
| 20090126015 | Monastyrsky et al. | May 2009 | A1 |
| 20090126016 | Sobko et al. | May 2009 | A1 |
| 20090133125 | Choi et al. | May 2009 | A1 |
| 20090144823 | Lamastra et al. | Jun 2009 | A1 |
| 20090158430 | Borders | Jun 2009 | A1 |
| 20090172815 | Gu et al. | Jul 2009 | A1 |
| 20090187992 | Poston | Jul 2009 | A1 |
| 20090193293 | Stolfo et al. | Jul 2009 | A1 |
| 20090199296 | Xie et al. | Aug 2009 | A1 |
| 20090228233 | Anderson et al. | Sep 2009 | A1 |
| 20090241187 | Troyansky | Sep 2009 | A1 |
| 20090241190 | Todd et al. | Sep 2009 | A1 |
| 20090265692 | Godefroid et al. | Oct 2009 | A1 |
| 20090271867 | Zhang | Oct 2009 | A1 |
| 20090300415 | Zhang et al. | Dec 2009 | A1 |
| 20090300761 | Park et al. | Dec 2009 | A1 |
| 20090328185 | Berg et al. | Dec 2009 | A1 |
| 20090328221 | Blumfield et al. | Dec 2009 | A1 |
| 20100005146 | Drako et al. | Jan 2010 | A1 |
| 20100011205 | McKenna | Jan 2010 | A1 |
| 20100017546 | Poo et al. | Jan 2010 | A1 |
| 20100031353 | Thomas et al. | Feb 2010 | A1 |
| 20100037314 | Perdisci et al. | Feb 2010 | A1 |
| 20100043073 | Kuwamura | Feb 2010 | A1 |
| 20100054278 | Stolfo et al. | Mar 2010 | A1 |
| 20100058474 | Hicks | Mar 2010 | A1 |
| 20100064044 | Nonoyama | Mar 2010 | A1 |
| 20100077481 | Polyakov et al. | Mar 2010 | A1 |
| 20100083376 | Pereira et al. | Apr 2010 | A1 |
| 20100100718 | Srinivasan | Apr 2010 | A1 |
| 20100115621 | Staniford et al. | May 2010 | A1 |
| 20100132038 | Zaitsev | May 2010 | A1 |
| 20100154056 | Smith et al. | Jun 2010 | A1 |
| 20100180344 | Malyshev et al. | Jul 2010 | A1 |
| 20100192223 | Ismael et al. | Jul 2010 | A1 |
| 20100220863 | Dupaquis et al. | Sep 2010 | A1 |
| 20100235831 | Dittmer | Sep 2010 | A1 |
| 20100251104 | Massand | Sep 2010 | A1 |
| 20100281102 | Chinta et al. | Nov 2010 | A1 |
| 20100281541 | Stolfo et al. | Nov 2010 | A1 |
| 20100281542 | Stolfo et al. | Nov 2010 | A1 |
| 20100287260 | Peterson et al. | Nov 2010 | A1 |
| 20100299754 | Amit et al. | Nov 2010 | A1 |
| 20100306173 | Frank | Dec 2010 | A1 |
| 20110004737 | Greenebaum | Jan 2011 | A1 |
| 20110025504 | Lyon et al. | Feb 2011 | A1 |
| 20110041179 | St Hlberg | Feb 2011 | A1 |
| 20110047594 | Mahaffey et al. | Feb 2011 | A1 |
| 20110047620 | Mahaffey et al. | Feb 2011 | A1 |
| 20110055907 | Narasimhan et al. | Mar 2011 | A1 |
| 20110078794 | Manni et al. | Mar 2011 | A1 |
| 20110093951 | Aziz | Apr 2011 | A1 |
| 20110099620 | Stavrou et al. | Apr 2011 | A1 |
| 20110099633 | Aziz | Apr 2011 | A1 |
| 20110113231 | Kaminsky | May 2011 | A1 |
| 20110145918 | Jung et al. | Jun 2011 | A1 |
| 20110145920 | Mahaffey et al. | Jun 2011 | A1 |
| 20110145934 | Abramovici et al. | Jun 2011 | A1 |
| 20110167493 | Song et al. | Jul 2011 | A1 |
| 20110167494 | Bowen et al. | Jul 2011 | A1 |
| 20110173460 | Ito et al. | Jul 2011 | A1 |
| 20110219449 | St. Neitzel et al. | Sep 2011 | A1 |
| 20110219450 | McDougal et al. | Sep 2011 | A1 |
| 20110225624 | Sawhney et al. | Sep 2011 | A1 |
| 20110225655 | Niemela et al. | Sep 2011 | A1 |
| 20110247072 | Staniford et al. | Oct 2011 | A1 |
| 20110265182 | Peinado et al. | Oct 2011 | A1 |
| 20110289582 | Kejriwal et al. | Nov 2011 | A1 |
| 20110302587 | Nishikawa et al. | Dec 2011 | A1 |
| 20110307954 | Melnik et al. | Dec 2011 | A1 |
| 20110307955 | Kaplan et al. | Dec 2011 | A1 |
| 20110307956 | Yermakov et al. | Dec 2011 | A1 |
| 20110314546 | Aziz et al. | Dec 2011 | A1 |
| 20120023593 | Puder et al. | Jan 2012 | A1 |
| 20120054869 | Yen et al. | Mar 2012 | A1 |
| 20120066698 | Yanoo | Mar 2012 | A1 |
| 20120079596 | Thomas et al. | Mar 2012 | A1 |
| 20120084859 | Radinsky et al. | Apr 2012 | A1 |
| 20120110667 | Zubrilin et al. | May 2012 | A1 |
| 20120117652 | Manni et al. | May 2012 | A1 |
| 20120121154 | Xue et al. | May 2012 | A1 |
| 20120124426 | Maybee et al. | May 2012 | A1 |
| 20120174186 | Aziz et al. | Jul 2012 | A1 |
| 20120174196 | Bhogavilli et al. | Jul 2012 | A1 |
| 20120174218 | McCoy et al. | Jul 2012 | A1 |
| 20120198279 | Schroeder | Aug 2012 | A1 |
| 20120210423 | Friedrichs et al. | Aug 2012 | A1 |
| 20120222121 | Staniford et al. | Aug 2012 | A1 |
| 20120255015 | Sahita et al. | Oct 2012 | A1 |
| 20120255017 | Sallam | Oct 2012 | A1 |
| 20120260342 | Dube et al. | Oct 2012 | A1 |
| 20120266244 | Green et al. | Oct 2012 | A1 |
| 20120278886 | Luna | Nov 2012 | A1 |
| 20120297489 | Dequevy | Nov 2012 | A1 |
| 20120330801 | McDougal et al. | Dec 2012 | A1 |
| 20130014259 | Gribble et al. | Jan 2013 | A1 |
| 20130036472 | Aziz | Feb 2013 | A1 |
| 20130047257 | Aziz | Feb 2013 | A1 |
| 20130074185 | McDougal et al. | Mar 2013 | A1 |
| 20130086684 | Mohler | Apr 2013 | A1 |
| 20130097699 | Balupari et al. | Apr 2013 | A1 |
| 20130097706 | Titonis et al. | Apr 2013 | A1 |
| 20130111587 | Goel et al. | May 2013 | A1 |
| 20130117852 | Stute | May 2013 | A1 |
| 20130117855 | Kim et al. | May 2013 | A1 |
| 20130139264 | Brinkley et al. | May 2013 | A1 |
| 20130160125 | Likhachev et al. | Jun 2013 | A1 |
| 20130160127 | Jeong et al. | Jun 2013 | A1 |
| 20130160130 | Mendelev et al. | Jun 2013 | A1 |
| 20130160131 | Madou et al. | Jun 2013 | A1 |
| 20130167236 | Sick | Jun 2013 | A1 |
| 20130174214 | Duncan | Jul 2013 | A1 |
| 20130185789 | Hagiwara et al. | Jul 2013 | A1 |
| 20130185795 | Winn et al. | Jul 2013 | A1 |
| 20130185798 | Saunders et al. | Jul 2013 | A1 |
| 20130191915 | Antonakakis et al. | Jul 2013 | A1 |
| 20130196649 | Paddon et al. | Aug 2013 | A1 |
| 20130227691 | Aziz et al. | Aug 2013 | A1 |
| 20130246370 | Bartram et al. | Sep 2013 | A1 |
| 20130263260 | Mahaffey et al. | Oct 2013 | A1 |
| 20130291109 | Staniford et al. | Oct 2013 | A1 |
| 20130298243 | Kumar et al. | Nov 2013 | A1 |
| 20140053260 | Gupta et al. | Feb 2014 | A1 |
| 20140053261 | Gupta et al. | Feb 2014 | A1 |
| 20140130158 | Wang et al. | May 2014 | A1 |
| 20140137180 | Lukacs et al. | May 2014 | A1 |
| 20140169762 | Ryu | Jun 2014 | A1 |
| 20140179360 | Jackson et al. | Jun 2014 | A1 |
| 20140328204 | Klotsche et al. | Nov 2014 | A1 |
| 20140337836 | Ismael | Nov 2014 | A1 |
| 20140351935 | Shao et al. | Nov 2014 | A1 |
| 20150096025 | Ismael | Apr 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 2439806 | Jan 2008 | GB |
| 2490431 | Oct 2012 | GB |
| 0206928 | Jan 2002 | WO |
| 0223805 | Mar 2002 | WO |
| 2007022454 | Feb 2007 | WO |
| 2007117636 | Oct 2007 | WO |
| 2008041950 | Apr 2008 | WO |
| 2008084259 | Jul 2008 | WO |
| 2011084431 | Jul 2011 | WO |
| 2011112348 | Sep 2011 | WO |
| 2012075336 | Jun 2012 | WO |
| 2012145066 | Oct 2012 | WO |
| 2013067505 | May 2013 | WO |
| 2014057542 | Apr 2014 | WO |
| Entry |
|---|
| Adobe Systems Incorporated, “PDF 32000-1:2008, Document management—Portable document format—Part1:PDF 1.7”, First Edition, Jul. 1, 2008, 756 pages. |
| Apostolopoulos, George; hassapis, Constantinos; “V-eM: A cluster of Virtual Machines for Robust, Detailed, and High-Performance Network Emulation”, 14th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems, Sep. 11-14, 2006, pp. 117-126. |
| Clark, John, Sylvian Leblanc,and Scott Knight. “Risks associated with usb hardware trojan devices used by insiders.” Systems Conference (SysCon), 2011 IEEE International. IEEE, 2011. |
| FireEye Malware Analysis & Exchange Network, Malware Protection System, FireEye Inc., 2010. |
| FireEye Malware Analysis, Modern Malware Forensics, FireEye Inc., 2010. |
| FireEye v.6.0 Security Target, pp. 1-35, Version 1.1, FireEye Inc., May 2011. |
| Gibler, Clint, et al. AndroidLeaks: automatically detecting potential privacy leaks in android applications on a large scale. Springer Berlin Heidelberg, 2012. |
| Gregg Keizer: “Microsoft's HoneyMonkeys Show Patching Windows Works”, Aug. 8, 2005, XP055143386, Retrieved from the Internet: URL:https://web.archive.org/web/20121022220617/http://www.informationweek- .com/microsofts-honeymonkeys-show-patching-wi/167600716 [retrieved on Sep. 29, 2014]. |
| Heng Yin et al, Panorama: Capturing System-Wide Information Flow for Malware Detection and Analysis, Research Showcase @ CMU, Carnegie Mellon University, 2007. |
| Idika et al., A-Survey-of-Malware-Detection-Techniques, Feb. 2, 2007, Department of Computer Science, Purdue University. |
| Isohara, Takamasa, Keisuke Takemori, and Ayumu Kubota. “Kernel-based behavior analysis for android malware detection.” Computational intelligence and Security (CIS), 2011 Seventh International Conference on. IEEE, 2011. |
| Kevin A Roundy et al: “Hybrid Analysis and Control of Malware”, Sep. 15, 2010, Recent Advances in Intrusion Detection, Springer Berlin Heidelberg, Berlin, Heidelberg, pp. 317-338, XP019150454 ISBN:978-3-642-15511-6. |
| Leading Colleges Select FireEye to Stop Malware-Related Data Breaches, FireEye Inc., 2009. |
| Li et al., A VMM-Based System Call Interposition Framework for Program Monitoring, Dec. 2010, IEEE 16th International Conference on Parallel and Distributed Systems, pp. 706-711. |
| Lindorfer, Martina, Clemens Kolbitsch, and Paolo Milani Comparetti. “Detecting environment-sensitive malware.” Recent Advances in Intrusion Detection. Springer Berlin Heidelberg, 2011. |
| Mori, Detecting Unknown Computer Viruses, 2004, Springer-Verlag Berlin Heidelberg. |
| Oberheide et al., CloudAV.sub.—N-Version Antivirus in the Network Cloud, 17th USENIX Security Symposium USENIX Security '08 Jul. 28-Aug. 1, 2008 San Jose, CA. |
| Wahid et al., Characterising the Evolution in Scanning Activity of Suspicious Hosts, Oct. 2009, Third International Conference on Network and System Security, pp. 344-350. |
| Yuhei Kawakoya et al: “Memory behavior-based automatic malware unpacking in stealth debugging environment”, Malicious and Unwanted Software (Malware), 2010 5th International Conference on, IEEE, Piscataway, NJ, USA, Oct. 19, 2010, pp. 39-46, XP031833827, ISBN:978-1-4244-8-9353-1. |
| Zhang et al., The Effects of Threading, Infection Time, and Multiple-Attacker Collaboration on Malware Propagation, Sep. 2009, IEEE 28th International Symposium on Reliable Distributed Systems, pp. 73-82. |
| Anonymous, “Inside Adobe Reader Protected 1 Mode—Part 1”—Design, Oct. 5, 2010, Retrieved from the Internet: URL:http://blogs.adobe.com/security/2010/1O/inside-adobe-reader-protected-mode-part-1-design.html [retrieved on May 6, 2014]. |
| Didier Stevens: “Malicious PDF Documents Explained”, Security & Privacy, IEEE, IEEE Service Center, Los Alamitos, CA, US, vol. 9, No. L, Jan. 1, 2011. |
| EP 12736373.7 Filed Jan. 19, 2012 Extended European Search Report dated May 21, 2014. |
| PCT/US2012/021916 filed Jan. 19, 2012, International Search Report and Written Opinion dated May 10, 2012. |
| Rautiainen et al. “A Look at Portable Document Format Vulnerabilities”, Information Security Technical Report, Elsevier Advanced Technology, Amsterdam, NL, vol. 14, No. L, Feb. 1, 2009. |
| “Network Security: NetDetector—Network Intrusion Forensic System (NIFS) Whitepaper”, (“NetDetector Whitepaper”), (2003). |
| “Packet”, Microsoft Computer Dictionary, Microsoft Press, (Mar. 2002), 1 page. |
| “When Virtual is Better Than Real”, IEEEXplore Digital Library, available at, http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumbe- r=990073, (Dec. 7, 2013). |
| Abdullah, et al., Visualizing Network Data for Intrusion Detection, 2005 IEEE Workshop on Information Assurance and Security, pp. 100-108. |
| Adetoye, Adedayo , et al., “Network Intrusion Detection & Response System”, (“Adetoye”), (Sep. 2003). |
| AltaVista Advanced Search Results. “attack vector identifier”. Http://www.altavista.com/web/results?Itag=ody&pg=aq&aqmode=aqa=Event+Orch- estrator . . . , (Accessed on Sep. 15, 2009). |
| AltaVista Advanced Search Results. “Event Orchestrator”. Http://www.altavista.com/web/results?Itag=ody&pg=aq&aqmode=aqa=Event+Orch- esrator . . . , (Accessed on Sep. 3, 2009). |
| Aura, Tuomas, “Scanning electronic documents for personally identifiable information”, Proceedings of the 5th ACM workshop on Privacy in electronic society. ACM, 2006. |
| Baecher, “The Nepenthes Platform: An Efficient Approach to collect Malware”, Springer-verlag Berlin Heidelberg, (2006), pp. 165-184. |
| Baldi, Mario; Risso, Fulvio; “A Framework for Rapid Development and Portable Execution of Packet-Handling Applications”, 5th IEEE International Symposium Processing and Information Technology, Dec. 21, 2005, pp. 233-238. |
| Bayer, et al., “Dynamic Analysis of Malicious Code”, J Comput Virol, Springer-Verlag, France., (2006), pp. 67-77. |
| Boubalos, Chris , “extracting syslog data out of raw pcap dumps, seclists.org, Honeypots mailing list archives”, available at http://seclists.org/honeypots/2003/q2/319 (“Boubalos”), (Jun. 5, 2003). |
| Chaudet, C. , et al., “Optimal Positioning of Active and Passive Monitoring Devices”, International Conference on Emerging Networking Experiments and Technologies, Proceedings of the 2005 ACM Conference on Emerging Network Experiment and Technology, CoNEXT '05, Toulousse, France, (Oct. 2005), pp. 71-82. |
| Cisco “Intrusion Prevention for the Cisco ASA 5500-x Series” Data Sheet (2012). |
| Cisco, Configuring the Catalyst Switched Port Analyzer (SPAN) (“Cisco”), (1992-2003). |
| Cohen, M.I. , “PyFlag—An advanced network forensic framework”, Digital investigation 5, Elsevier, (2008), pp. S112-S120. |
| Costa, M. , et al., “Vigilante: End-to-End Containment of Internet Worms”, SOSP '05, Association for Computing Machinery, Inc., Brighton U.K., (Oct. 23-26, 2005). |
| Crandall, J.R. , et al., “Minos:Control Data Attack Prevention Orthogonal to Memory Model”, 37th International Symposium on Microarchitecture, Portland, Oregon, (Dec. 2004). |
| Deutsch, P. , “Zlib compressed data format specification version 3.3” RFC 1950, (1996). |
| Distler, “Malware Analysis: An Introduction”, SANS Institute InfoSec Reading Room, SANS Institute, (2007). |
| Dunlap, George W. , et al., “ReVirt: Enabling Intrusion Analysis through Virtual-Machine Logging and Replay”, Proceeding of the 5th Symposium on Operating Systems Design and Implementation, USENIX Association, (“Dunlap”), (Dec. 9, 2002). |
| Excerpt regarding First Printing Date for Merike Kaeo, Designing Network Security (“Kaeo”), (2005). |
| Filiol, Eric , et al., “Combinatorial Optimisation of Worm Propagation on an Unknown Network”, International Journal of Computer Science 2.2 (2007). |
| Goel, et al., Reconstructing System State for Intrusion Analysis, Apr. 2008 SIGOPS Operating Systems Review, vol. 42 Issue 3, pp. 21-28. |
| Hjelmvik, Erik , “Passive Network Security Analysis with NetworkMiner”, (IN)Secure, Issue 18, (Oct. 2008), pp. 1-100. |
| IEEE Xplore Digital Library Sear Results for “detection of unknown computer worms”. Http//ieeexplore.ieee.org/searchresult.jsp?SortField=Score&SortOrder=desc- &ResultC . . . , (Accessed on Aug. 28, 2009). |
| Kaeo, Merike , “Designing Network Security”, (“Kaeo”), (Nov. 2003). |
| Kim, H. , et al., “Autograph: Toward Automated, Distributed Worm Signature Detection”, Proceedings of the 13th Usenix Security Symposium (Security 2004), San Diego, (Aug. 2004), pp. 271-286. |
| Krasnyansky, Max , et al., Universal TUN/TAP driver, available at https://www.kernel.org/doc/Documentation/networking/tuntap.txt (2002) (“Krasnyansky”). |
| Kreibich, C. , et al., “Honeycomb—Creating Intrusion Detection Signatures Using Honeypots”, 2nd Workshop on Hot Topics in Networks (HotNets-11), Boston, USA, (2003). |
| Kristoff, J. , “Botnets, Detection and Mitigation: DNS-Based Techniques”, NU Security Day, (2005), 23 pages. |
| Liljenstam, Michael , et al., “Simulating Realistic Network Traffic for Worm Warning System Design and Testing”, Institute for Security Technology studies, Dartmouth College (“Liljenstam”), (Oct. 27, 2003). |
| Lok Kwong et al: “DroidScope: Seamlessly Reconstructing the OS and Dalvik Semantic Views for Dynamic Android Malware Analysis”, Aug. 10, 2012, XP055158513, Retrieved from the Internet: URL:https://www.usenix.org/system/files/conference/usenixsecurity12/sec12- -final107.pdf [retrieved on Dec. 15, 2014]. |
| Marchette, David J., “Computer Intrusion Detection and Network Monitoring: A Statistical Viewpoint”, (“Marchette”), (2001). |
| Margolis, P.E. , “Random House Webster's ‘Computer & Internet Dictionary 3rd Edition’”, ISBN 0375703519, (Dec. 1998). |
| Moore, D. , et al., “Internet Quarantine: Requirements for Containing Self-Propagating Code”, INFOCOM, vol. 3, (Mar. 30-Apr. 3, 2003), pp. 1901-1910. |
| Morales, Jose A., et al., ““Analyzing and exploiting network behaviors of malware.””, Security and Privacy in Communication Networks. Springer Berlin Heidelberg, 2010. 20-34. |
| Natvig, Kurt , “SANDBOXII: Internet”, Virus Bulletin Conference, (“Natvig”), (Sep. 2002). |
| NetBIOS Working Group. Protocol Standard for a NetBIOS Service on a TCP/UDP transport: Concepts and Methods. STD 19, RFC 1001, Mar. 1987. |
| Newsome, J. , et al., “Dynamic Taint Analysis for Automatic Detection, Analysis, and Signature Generation of Exploits on Commodity Software”, In Proceedings of the 12th Annual Network and Distributed System Security, Symposium (NDSS '05), (Feb. 2005). |
| Newsome, J. , et al., “Polygraph: Automatically Generating Signatures for Polymorphic Worms”, In Proceedings of the IEEE Symposium on Security and Privacy, (May 2005). |
| Nojiri, D. , et al., “Cooperation Response Strategies for Large Scale Attack Mitigation”, DARPA Information Survivability Conference and Exposition, vol. 1, (Apr. 22-24, 2003), pp. 293-302. |
| Reiner Sailer, Enriquillo Valdez, Trent Jaeger, Roonald Perez, Leendert van Doom, John Linwood Griffin, Stefan Berger., sHype: Secure Hypervisor Appraoch to Trusted Virtualized Systems (Feb. 2, 2005) (“Sailer”). |
| Silicon Defense, “Worm Containment in the Internal Network”, (Mar. 2003), pp. 1-25. |
| Singh, S. , et al., “Automated Worm Fingerprinting”, Proceedings of the ACM/USENIX Symposium on Operating System Design and Implementation, San Francisco, California, (Dec. 2004). |
| Spitzner, Lance , “Honeypots: Tracking Hackers”, (“Spizner”), (Sep. 17, 2002). |
| The Sniffers's Guide to Raw Traffic available at: yuba.stanford.edu/.about.casado/pcap/section1.html, (Jan. 6, 2014). |
| Thomas H. Ptacek, and Timothy N. Newsham , “Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection”, Secure Networks, (“Ptacek”), (Jan. 1998). |
| U.S. Pat. No. 8,171,553 filed Apr. 20, 2006, Inter Parties Review Decision dated Jul. 10, 2015. |
| U.S. Pat. No. 8,291,499 filed Mar. 16, 2012, Inter Parties Review Decision dated Jul. 10, 2015. |
| Venezia, Paul , “NetDetector Captures Intrusions”, InfoWorld Issue 27, (“Venezia”), (Jul. 14, 2003). |
| Whyte, et al., “DNS-Based Detection of Scanning Works in an Enterprise Network”, Proceedings of the 12th Annual Network and Distributed System Security Symposium, (Feb. 2005), 15 pages. |
| Williamson, Matthew M., “Throttling Viruses: Restricting Propagation to Defeat Malicious Mobile Code”, ACSAC Conference, Las Vegas, NV, USA, (Dec. 2002), pp. 1-9. |
| Chen, P. M. and Noble, B. D., “When Virtual is Better Than Real, Department of Electrical Engineering and Computer Science”, University of Michigan (“Chen”), 2001. |
| King, Samuel T., et al., “Operating System Support for Virtual Machines”, (“King”) (2003). |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13011344 | Jan 2011 | US |
| Child | 14673292 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12263971 | Nov 2008 | US |
| Child | 13011344 | US |
