Referrer context identification for remote object links

A computer, computer program product, and method identify referrer context information associated with a remote object link. A network inspection module monitors network traffic and a remote object link identification module identifies remote links and their associated referrer context information. A link storage module stores the referrer context information along with the associated link. A look up module looks up the referrer context information in response to a request for a source of a link. The referrer context information is an important security resource in identifying the true source of a threat, and in avoiding future attacks. In addition, it allows for a more complete picture of how a link moves from one client to another by tracking how the link was sent and received.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains in general to computer security and in particular to identifying referrer information for a remote object link received via a network.

2. Description of the Related Art

Applications executed on modern computers are often susceptible to a wide variety of network-based attacks. Web browsers, for example, are particularly susceptible to attacks because browsers receive large amounts of content from the Internet. Other types of applications are also vulnerable. For example, email programs and even word processors provide interfaces for executing network-based content.

Malicious attackers can compromise such applications by crafting specially-formulated input that exploits vulnerabilities in the programs. This input contains code that, when executed, gives the attackers control over the applications and allows them to perform malicious acts such as capturing keystrokes, sending messages on the network, deleting files, installing malicious software (malware) such as spyware and adware, etc.

Many such malicious attacks are received at the computer as remote object links in network traffic received via various protocols, such as email, instant messaging, or HTTP associated with a website. Traditional threat analysis, detection, repair, and avoidance systems lack the ability to reliably identify the referrer, or sender, to a remote object associated with a link received in the network traffic.

BRIEF SUMMARY

The above and other needs are met by a computer, computer program product, and method for identifying referrer context information associated with a remote object link. Embodiments of the computer and computer program product comprise a network inspection module that monitors network traffic, a remote object link identification module that identifies remote links in traffic and the associated referrer context information, and a look up module for looking up referrer context information in response to a request for a source of a link. The embodiments also comprise a link storage module that stores the referrer context information along with the associated link. Referrer context information includes information allowing the entity that provided the link to be ascertained. The referrer context information is an important resource in identifying the true source of a threat, and in avoiding future attacks. In addition, it allows for a more complete picture of how a link moves from one client to another by tracking how the link was received and sent.

Embodiments of the method comprise identifying remote links in network traffic and their associated referrer context information, storing the referrer context information, and looking up the referrer context information in response to a request for a source of a link.

DETAILED DESCRIPTION

FIG. 1is a high-level block diagram of a computing environment100according to one embodiment.FIG. 1illustrates a client105connected via a network inspection module110, to a network115for, among other things, accessing a remote object120. The client105also may communicate with a server125and a global referral system130via the network115. Only one client105, one remote object120, and one server125are shown inFIG. 1in order to simplify and clarify the description.

Embodiments of the computing environment100can have thousands or millions of clients105, remote objects120, and servers125connected to the network115.

In one embodiment, the client105, or client device, is a computer used by one or more users to connect to the network115and various network entities, such as remote objects120, servers125, and a global referrer system130. The client105, for example, can be a personal computer or other network-capable device like a personal digital assistant (PDA), mobile telephone, pager, or television “set-top box.” For purposes of this description, the term “client” also includes computers such as servers and gateways that have the characteristics described herein.

The client105executes one or more applications such as a web browser, email program, word processor, spreadsheet, image viewer, or music player. The application has an interface for executing content received via the network115, stored on a local disk, or located elsewhere. In a common example, the application is a web browser such as MICROSOFT INTERNET EXPLORER or MOZILLA FIREFOX that includes functionality for downloading web pages, e.g., from a server120and executing scripts written in VBScript or JavaScript contained therein. Some content downloaded and/or accessed by an application contains malicious code that attempts to exploit a vulnerability in the application or otherwise attack the client105.

A network inspection module110monitors network traffic to and from the client105, for all ports or a subset thereof. The network inspection module110may be a network proxy, local or remote to the client105, or may be a network appliance. Thus, according to one embodiment, the network inspection module110may be integrated with client105. Alternatively, the network inspection module110may be implemented as multiple plug-ins to network applications, such as to a web browser, email client, news reader, RDF Site Summary (RSS) feed hander, IM client, and the like. The network inspection module110captures network traffic and hands it off to a global referrer system130.

A global referrer system130detects links to remote objects120within network traffic received from the network inspection module110and identifies context information about the referrers of the links. For example, for a link received at (or sent by) a client105via email, the global referrer system130identifies the link in the incoming (outgoing) email and identifies and stores referrer context information for the received (sent) link. Referrer context information, in a general sense, is information allowing the entity that provided—or received—the link to be ascertained. Thus, the referrer context information may include transmission context information as well, e.g., for links sent from the client device. As used herein, referrer context information includes information about the context in which the link was sent or received, e.g., if sent or received via a server, such as for SMS and newsgroup messages, identification of the server. Referrer context information also includes, for some protocols, a user identification, e.g., a user name or email address. For HTTP, referrer context information includes a URL. Thus, the content of the referrer context information is specific to the particular protocol in which the link was sent or received. For a link sent or received via Instant Messaging (IM) or Internet Relay Chat (IRC), the referrer context information includes a server and a user name; for Network News Transfer Protocol (NNTP), the referrer context information includes a server, a newsgroup, a posted, and a poster; for email, the referrer context information includes an email address (i.e., an email name and email domain in the form of emailname@emaildomain) and for a link sent or received via HTTP, the referrer context information includes a URL. Thus, referrer context information may include a direction associated with the network traffic (e.g., inbound or outbound), a protocol, the remote link itself, the referrer (sender) and recipient (receiver), transmission associated data (server, etc.), time of transmission, time of receipt, and the like. When referrer information associated with the link is request by the client105or a third party, the global referrer system130allows for a look up of the stored referrer context information.

The network115represents the communication pathways between the client105and various network entities such as remote objects120, servers125, and the global referrer system130. In one embodiment, the network115is the Internet. The network115can also utilize dedicated or private communications links that are not necessarily part of the Internet. In one embodiment, the network115uses standard communications technologies and/or protocols such as Ethernet, 802.11, etc. Similarly, the networking protocols used on the network115can include the transmission control protocol/Internet protocol (TCP/IP), the hypertext transport protocol (HTTP), the simple mail transfer protocol (SMTP), the file transfer protocol (FTP), etc. The data exchanged over the network115can be represented using technologies and/or formats including the hypertext markup language (HTML), the extensible markup language (XML), etc. In addition, all or some of links can be encrypted using conventional encryption technologies such as the secure sockets layer (SSL), Secure HTTP and/or virtual private networks (VPNs). In another embodiment, the entities can use custom and/or dedicated data communications technologies instead of, or in addition to, the ones described above.

A remote object120is content, e.g., web content, to which a link points, such as a webpage, a downloadable file, scripts written in interpreted languages such as VBScript and JavaScript, executable programs, images, music, multimedia content, and the like. In some instances, a remote object may include malicious code posing a threat to the client105. For example, the remote object120may be a seemingly-innocuous web page that includes a malicious script. The script, when executed by the client105, attempts to compromise the client105, e.g, by exploiting a vulnerability of the client105or its applications.

A server125provides content, including remote objects120, to the client105via the network115. In one embodiment, the server125is a web server that provides content such as HTML web pages. In other embodiments, the server125is a different type of server, such as a server dedicated to providing a specific type of content. In some instances, the server125may surreptitiously provide malicious code to the client105, for example, as contained in a remote object120as discussed above.

FIG. 2is a high-level block diagram illustrating a typical computer200for use as a client105or server125, or for use as a network appliance or proxy such as network inspection module according to one embodiment. Illustrated are a processor202coupled to a bus204. Also coupled to the bus204are a memory206, a storage device208, a keyboard210, a graphics adapter212, a pointing device214, and a network adapter216. A display218is coupled to the graphics adapter212.

The processor202may be any general-purpose processor such as an INTEL x86 compatible-CPU. The storage device208is, in one embodiment, a hard disk drive but can also be any other device capable of storing data, such as a writeable compact disk (CD) or DVD, or a solid-state memory device. The memory206may be, for example, firmware, read-only memory (ROM), non-volatile random access memory (NVRAM), and/or RAM, and holds instructions and data used by the processor202. The pointing device214may be a mouse, track ball, or other type of pointing device, and is used in combination with the keyboard210to input data into the computer200. The graphics adapter212displays images and other information on the display218. The network adapter216couples the computer200to the network114.

The types of computers200utilized by the entities ofFIG. 1can vary depending upon the embodiment and the processing power utilized by the entity. For example, a client105that is a mobile device such as a PDA typically has limited processing power, a small display218, and might lack a pointing device214. The server125, in contrast, may comprise multiple blade servers working together.

As is known in the art, the computer200is adapted to execute computer program modules. As used herein, the term “module” refers to computer program logic and/or data for providing the specified functionality. A module can be implemented in hardware, firmware, and/or software. In one embodiment, the modules are stored on the storage device208, loaded into the memory206, and executed by the processor202.

In addition, this description uses the term “application” to refer to a program executed by the computer200. The application is formed of one or more files that typically reside on the storage device208and are loaded into memory206when executed. At least one of the files loaded into memory206is referred to as the “executable image” and is executed as a process. The computer200has a state that is defined by the content of the memory208, values stored in registers of the processor202, and/or other data within the computer at a given instant.

FIG. 3is a block diagram illustrating a detailed view of a global referrer system130according to one embodiment. In some embodiments the global referrer system130is incorporated into an operating system executing on the client105while in other embodiments the global referrer system130may be a standalone application or part of another product according to various embodiments. As shown inFIG. 3, the global referrer system130itself includes multiple modules. Those of skill in the art will recognize that other embodiments of the global referrer system130can have different and/or other modules than the ones described here, and that the functionalities can be distributed among the modules in a different manner.

The global referrer system130includes a remote object link identification module310, a link storage module315, and a look up module320according to one embodiment.

A remote object link identification module310identifies remote links in network traffic, e.g., links to remote objects120received from the network inspection module110. The remote links may be Uniform Resource Locators (URLs) for identifying remote objects120on the Internet or network115or Universal Naming Conventions (UNCs) for describing the location of a network resource, such as a shared file, directory, or printer. However, the remote links may be any string or binary data that represents a location of a remote object120. The remote object link identification module310is configured to identify associated referrer context information for the remote links from a plurality of protocols. The protocols include, but are not limited to, standard and secure Hypertext Transfer Protocol (HTTP, HTTPs), Short Message Service (SMS), NNTP, Network Time Protocol (NTP), Simple Network Management Protocol (SNMP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Internet Control Message Protocol (ICMP), Venturi Transport Protocol (VTP), Real-time Transport Protocol (RTP), Stream Control Transmission Protocol (SCTP), and Telnet.

The remote object link identification module310uses pattern matching to locate remote links in the network traffic. In one embodiment, the remote object link identification module310uses regular expression searching may be used to identify remote links in the network traffic.

In addition to identifying the links themselves, the remote object link identification module310extracts referrer context information associated with the referrer that provided the remote link for an incoming link. The referrer context information is specific to the protocol that the remote link was found on. For example, for a link received via HTTP, the referrer context information includes a URL; for Instant Messaging (IM) or Internet Relay Chat (IRC), the referrer context information includes a server and a user name; and for Network News Transfer Protocol (NNTP), the referrer context information includes a server, a newsgroup, a posted, and a poster. Thus, for some protocols, the referrer context information includes an identifier of the referrer, for example a user name for IM or IRC.

For remote object source protocols that result in a file being stored on at least one storage medium, source information may be stored in an alternate file stream or as attributes attached to or associated with the file. For other remote source protocols, a custom source tagging process may be necessary to associate the remote object120with the referrer context information. A source tag, as used herein, includes the referrer context information to be associated with the remote object link, and is the manner in which this information is tied to the link.

The remote object link identification module310also identifies links in outbound network traffic. In this context, the referrer context information may include information associated with the recipient of the remote link. Thus, referrer context information may include a direction associated with the network traffic (e.g., inbound or outbound), a protocol, the remote link itself, the referrer (sender) and recipient (receiver), time of transmission, time of receipt, and the like.

Once a remote link and associated referrer context information are identified, the remote object link identification module310sends the link and the referrer context information to a link storage module315.

A link storage module315stores remote links and associated referrer context information received from the remote object link identification module310. The link storage module315is a relational database according to one embodiment. Alternatively, the link storage module315may be an Extensible Markup Language (XML) file, text file, or any other data storage module. In some embodiments, the link storage module315is integrated with the other portions of the global referrer system130on the same device, e.g., client device or network proxy. Alternatively, the link storage module315may be implemented on a separate device from the monitoring functionality of the network inspection module110, as indicated by the dashed line surrounding the link storage module.

A look up module320provides access to the remote links and referrer context information stored in the link storage module315. Specifically, in response to a request for the source of a remote link, the look up module320accesses the link storage module315and returns the remote link referrer context information. The request for the referrer context information may include source tag information as described herein. Alternatively, the source information for the remote object120may be stored locally, for example in an alternate source stream in the case of downloading a file from a website using a Windows operating system. The request results from an attack on the client105, or detection of malicious code associated with a remote object120. Alternatively, the request may result from detection of an outbound request for the remote object120, e.g., by the client105, using the associated remote link. The referrer context information retrieved can then be used for threat detection or other means requiring source data.

The above modules310-320need not be discrete modules. The configuration shown inFIG. 3is meant only by way of example and not limitation; other configurations are within the scope of the present invention.

FIG. 4is a flowchart illustrating steps performed by a global referrer system130according to one embodiment. Other embodiments perform the illustrated steps in different orders, and/or perform different or additional steps. Moreover, some or all of the steps can be performed by modules other than those referenced.

A network inspection module110monitors410s network traffic as it arrives at, or is transmitted from, a client105, either as a remote or local network proxy or network appliance. Remote links in network traffic410, e.g., links to remote objects120, are identified412by a remote object link identification module310. The remote links may be URLs, UNCs, or any string or binary data that represents a location of a remote object120. The remote object link identification module310uses regular expression searching or any other pattern matching technique to identify412the remote links in the network traffic410. For example, a user of client device105receives an IM text message from a friend, Bob, with a link to a remote object120. The remote object link identification module310identifies412the remote link in the message.

Referrer context information also is identified414for the remote link by the remote object link identification module310. The referrer context information is specific to the protocol on which the remote link was found, however, the remote object link identification module310can identify414referrer context information from any of a number of protocols. For some remote source protocols, the identifying414further includes a custom source tagging process for associating the remote object120with the referrer context information. In some embodiments, the time of transmission and the time of receipt of the remote link also are identified. The referrer context information is stored416, along with the link, at a link storage module315. Continuing with the above example, the remote object link identification module310identifies414the referrer context from the message received from Bob. In this case, the referrer context information includes Bob's user name, “IMTxtR,” and the server Bob used, “CoServ1.”

Some time later, a request418for the source of a remote link is received, from the client105or from a third party, e.g., via the network115. The request for the referrer context information may include source tag information. The request may result from, e.g., an attack on the client105, or detection of malicious code associated with a remote object120. Alternatively, the request may result from detection of an outbound request for the remote object120, e.g., by the client105, for accessing the associated remote link.

In response to the request418, the look up module320looks up420the stored referrer context information associated with the link, stored in the link storage module315. The referrer context information is provided422to the requestor. The retrieved referrer context information can then be used for threat detection or other means requiring source data.

The description in the specification is included to illustrate the operation of certain embodiments, is not all inclusive, and is not meant to limit the scope of the invention. The scope of the invention is to be limited only by the following claims. In particular, many additional features and variations will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter.