`Touboul
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006804 780B 1
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,804, 780 Bl
`*Oct. 12, 2004
`
`(54) SYSTEM AND METHOD FOR PROTECTING
`A COMPUTER AND A NETWORK FROM
`HOSTILE DOWNLOADABLES
`
`(75)
`
`Inventor: Shlomo Touboul, Kefar-haim (IL)
`
`(73) Assignee: Finjan Software, Ltd., Netanya (IL)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis(cid:173)
`claimer.
`
`(21) Appl. No.: 09/539,667
`
`(22) Filed:
`
`Mar. 30, 2000
`
`Related U.S. Application Data
`
`( 63) Continuation of application No. 08/964,388, filed on Nov. 6,
`1997, now Pat. No. 6,092,194.
`(60) Provisional application No. 60/030,639, filed on Nov. 8,
`1996.
`
`Int. Cl? ............................ H04L 9/00; G06F 11/30
`(51)
`(52) U.S. Cl. ....................... 713/181; 713/201; 713/176;
`717/178
`(58) Field of Search ................................. 713/200, 201,
`713/176, 181; 709/223, 225, 227, 229;
`717/168-178
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,077,677 A
`5,359,659 A
`5,361,359 A
`5,485,409 A
`5,485,575 A
`
`12/1991 Murphy et a!.
`10/1994 Rosenthal
`11/1994 Tajalli et a!.
`1!1996 Gupta et a!.
`1!1996 Chess et a!.
`
`. . . . . . . . . . . . . . . 703/27
`
`5,572,643 A
`5,579,509 A
`5,606,668 A
`5,623,600 A
`5,638,446 A
`5,692,047 A
`5,692,124 A
`5,720,033 A
`5,724,425 A
`5,740,248 A
`5,761,421 A
`
`11/1996 Judson
`* 11/1996 Furtney et a!.
`2/1997 Shwed
`4/1997 Ji et a!.
`6/1997 Rubin
`11/1997 McManis
`11/1997 Holden et a!.
`2/1998 Deo
`3/1998 Chang eta!.
`4/1998 Fieres et a!.
`6/1998 van Hoff et a!.
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`1091276 A1 * 4/2001
`1132796 A1 * 9/2001
`
`............. G06F/1!00
`............. G06F/1!00
`
`EP
`EP
`
`OTHER PUBLICATIONS
`
`Khare, "Microsoft Authenticode Analyzed" Jul. 22, 1996,
`xent.com/FoRK-archive/summer96/0338.html, p. 1-2. *
`
`(List continued on next page.)
`
`Primary Examiner-Ayaz Sheikh
`Assistant Examiner-Christopher Revak
`(74) Attorney, Agent, or Firm-Squire,
`Dempsey, L.L.P.
`
`(57)
`
`ABSTRACT
`
`Sanders &
`
`A computer-based method for generating a Downloadable
`ID to identify a Downloadable, including obtaining a Down(cid:173)
`loadable that includes one or more references to software
`components required by the Downloadable, fetching at least
`one software component identified by the one or more
`references, and performing a function on the Downloadable
`and the fetched software components to generate a Down(cid:173)
`loadable ID. A system and a computer-readable storage
`medium are also described and claimed.
`
`18 Claims, 10 Drawing Sheets
`
`800
`
`~
`
`Blue Coat Systems - Exhibit 1031
`
`
`
`US 6,804, 780 Bl
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`6/1998 Breslau et a!.
`5,765,205 A
`7/1998 Devarakonda et a!.
`5,784,459 A
`8/1998 Davis et a!.
`5,796,952 A
`9/1998 Cohen et a!.
`5,805,829 A
`11/1998 Chen et a!.
`5,832,208 A
`5,832,274 A * 11/1998 Cutler eta!. ................ 717/171
`12/1998 Angelo et a!.
`5,850,559 A
`5,859,966 A
`1!1999 Hayman eta!.
`5,864,683 A
`1!1999 Boebert et a!.
`5,892,904 A
`4/1999 Atkinson et a!.
`5,951,698 A
`9/1999 Chen et a!.
`5,956,481 A
`9/1999 Walsh et a!.
`5,974,549 A
`10/1999 Golan
`5,978,484 A * 11/1999 Apperson et a!. ............. 705/54
`5,983,348 A
`11/1999 Ji
`6,092,194 A * 7/2000 Touboul
`..................... 713/200
`6,154,844 A * 11/2000 Touboul et a!. ............. 713/201
`6,339,829 B1 * 1!2002 Beadle eta!. ............... 713/201
`
`01HER PUBLICATIONS
`
`"Release Notes for the Microsfot ActiveX Development
`Kit", Aug. 13, 1996, activex.adsp.or.jp/inetsdk/readme.txt,
`p. 1-10.*
`"Microsoft ActiveX Software Development Kit" Aug. 12,
`1996,
`activex.adsp.or.jp/inetsdk/help/overview.htm,
`p.
`1-6.*
`Doyle et al, "Microsoft Press Computer Dictionary" 1993,
`Microsoft Press, 2nd Edition, p. 137-138.*
`Schmitt, ".EXE. files, OS-2 style" Nov. 1988, PC Tech
`Journal via dialog search, vol. 6, #11, p. 76-78.*
`Jim K. Omura, "Novel Applications of Cryptography in
`Digital Communications", IEEE Communications Maga(cid:173)
`zine, May, 1990; pp. 21-29.
`Okamoto, E. et al., "ID-Based Authentication System For
`Computer Virus Detection", IEEE/IEE Electronic Library
`online, Electronics Letters, vol. 26, Issue 15, ISSN 0013/
`5194, Jul. 19, 1990, Abstract and pp. 1169-1170. URL:
`http://iel.ihs.com:80/cgi-bin/iel_cgi?se
`2ehts%26ViewTemplate%3ddocview%5fb%2ehts.
`IBM AntiVirus User's Guide Version 2.4, International
`Business Machines Corporation, Nov. 15, 1995, pp. 6-7.
`
`Norvin Leach et al, "IE 3.0 Applets Will Earn Certification",
`PC Week, vol. 13, No. 29, Jul. 22, 1996, 2 pages.
`"Finjan Software Releases SurfinBoard, Industry's First
`JAVA Security Product For the World Wide Web", Article
`published on the Internet by Finjan Softwre Ltd., Jul. 29,
`1996, 1 page.
`"Powerful PC Security for the New World of Java™ and
`Downloadables, Surfin Shield™" Article published on the
`Internet by Finjan Software Ltd., 1996, 2 Pages.
`Microsoft® Authenticode Technology, "Ensuring Account(cid:173)
`ability and Authenticity for Software Components on the
`Internet", Microsoft Corporation, Oct. 1996, including
`Abstract, Contents, Introduction and pp. 1-10.
`"Finjan Announces a Personal Java™ Firewall For Web
`Browsers-the SurfinShield™ 1.6 (formerly known as Surf(cid:173)
`inBoard)", Press Release of Finjan Releases SurfinShield
`1.6, Oct. 21, 1996, 2 pages.
`Company Profile "Finjan-Safe Surfing, The Java Security
`Solutions Provider", Article published on the Internet by
`Finjan Software Ltd., Oct. 31, 1996, 3 pages.
`"Finjan Announces Major Power Boost and New Features
`for SurfinShield™ 2.0" Las Vegas Convention Center/Pa(cid:173)
`vilion 5 P5551, Nov. 18, 1996, 3 pages.
`"Java Security: Issues & Solutions" Article published on the
`Internet by Finjan Software Ltd., 1996, 8 pages.
`"Products" Article published on the Internet, 7 pages.
`Mark LaDue, "Online Business Consulant: Java Security:
`Whose Business Is It?" Article published on the Internet,
`Home Page Press, Inc. 1996, 4 pages.
`Web Page Article "Frequently Asked Questions About
`Authenticode", Microsoft Corporation, last updated Feb. 17,
`1997, Printed Dec. 23, 1998. URL: http://www.microsoft.
`com/workshop/security I authcode/signfaq. asp#9, pp. 1-13.
`Zhang, X.N., "Secure Code Distribution", IEEE/IEE Elec(cid:173)
`tronic Library online, Computer, vol. 30, Issue 6, Jun., 1997,
`pp. 76-79.
`
`* cited by examiner
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 1 of 10
`
`US 6,804, 780 Bl
`
`100
`~
`
`105
`
`External Computer Network
`
`125
`
`110
`
`Internal Network
`Security System
`
`130
`
`115
`
`Internal Computer Network
`
`135
`
`120
`
`Security
`Management
`Console
`
`FIG. 1
`
`
`
`From
`External Computer
`Network 105
`
`110
`
`~
`
`125
`
`210
`
`vc!_
`
`External
`Communications
`Interface
`
`230
`
`!
`
`~40
`
`245
`
`Data Storage
`Device
`
`Security
`Database
`
`I Events Log
`
`I
`
`Users
`
`215
`
`L
`
`1/0 Interfaces
`
`220
`
`_!
`
`235
`
`!
`
`~5
`
`~50
`
`FIG. 2
`
`RAM
`
`Security
`Program
`
`Operating
`System
`
`205
`
`!
`
`CPU
`
`225
`
`L
`
`Internal
`Communications
`Interface
`
`130
`
`~
`
`To
`External Computer
`Network 115
`
`d •
`\Jl
`•
`~
`~ ......
`~ = ......
`
`0
`(')
`!"""
`'"""' ~N
`N c
`~
`
`'JJ. =(cid:173)~
`~ .....
`N
`0 ......,
`'"""' c
`
`e
`rJ'l
`-..a-..
`00
`Q
`~
`~
`00
`Q
`~
`1--"
`
`
`
`Security Database
`
`307
`
`309
`
`I
`I 240
`I
`~
`
`300
`
`~
`
`310
`
`305
`
`Security Policies
`
`r-
`
`1
`I
`I
`User ID, 1
`URL I
`Received :
`Downloadable 1
`I
`
`315
`
`317
`
`320
`
`ID
`Generator
`
`Policy
`Finder
`
`325
`
`Code
`Scanner
`
`Scanner
`
`340
`
`Path 1
`~
`
`Path 2 -ACL
`
`330
`
`I
`I
`I
`I
`I
`I Nonsuspicious
`: Downloadable
`I
`I
`
`I
`I
`I
`I
`I
`I
`
`Record
`keeping
`En~in,e
`
`Path 4
`~
`
`URL
`Comparator
`
`------------------------------
`FIG. 3
`
`- - - - - - - - - - - -- -
`
`i
`I 335
`---------------~
`350
`
`I
`
`245
`
`d •
`\Jl
`•
`~
`~ ......
`~ = ......
`
`0
`(')
`!"""
`"""" ~N
`N c
`~
`
`'JJ. =(cid:173)~
`~ .....
`
`~
`0 ......,
`"""" c
`
`e
`rJ'l
`-..a-..
`00
`Q
`~
`~
`00
`Q
`~
`1--"
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 4 of 10
`
`US 6,804, 780 Bl
`
`Security Policies
`305
`
`~
`
`405
`
`410
`
`415
`
`420
`
`425
`
`Policy Selectors
`
`Access Control
`Lists
`
`Trusted
`Certificate Lists
`
`URL Rule Bases
`
`Lists of Downloadables
`to Allow or Block per
`Administrative Override
`
`FIG. 4
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 5 of 10
`
`US 6,804, 780 Bl
`
`120
`
`To/From
`Internal Computer
`Network
`
`505
`~
`
`510
`
`Security
`Policy Ed it or
`
`Event Log
`Analysts
`Engine
`
`515
`~
`
`User
`Notification
`Engine
`
`FIG. 5
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 6 of 10
`
`US 6,804,780 Bl
`
`600
`
`~
`
`Start
`
`Receive Downloadable
`
`Generate Downloadable I D
`
`602
`
`604
`
`606
`
`630
`
`624
`
`FIG. 6A
`
`612
`
`Send results to
`Logical Engine
`
`End
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 7 of 10
`
`US 6,804, 780 Bl
`
`606
`
`~
`
`650
`
`No
`
`Security policy defined
`for User-ID and
`Downloadable?
`
`Yes
`
`Fetch the generic
`security policy for
`User 10
`
`652
`
`654
`
`Fetch the policy
`for
`User ID and
`Downloadable
`
`End
`
`FIG. 68
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 8 of 10
`
`US 6,804, 780 Bl
`
`655
`
`~
`
`Receive Results from First
`Comparator, ACL
`Comparator, Certificate
`Comparator and U RL
`Comparator
`
`Compare Results with
`Security Policies
`
`660
`
`662
`
`664
`
`Security Policies
`Confirm Pass?
`
`No
`>---------------~
`
`Yes
`
`666
`
`670
`
`Pass Downloadable
`
`Stop Downloadable
`
`Send Substitute
`Downloadble to
`Inform The User
`
`668
`
`Record Findings
`
`FIG. 6C
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 9 of 10
`
`US 6,804, 780 Bl
`
`628
`
`Start
`
`705
`
`710
`
`715
`
`No
`
`720
`
`Disassemble the Machine
`Code
`
`Resolve a Respective
`Command in The Code
`
`Is The Resolved
`Command Suspect?
`
`Decode and Register The
`Command and The
`Command Parameters as
`DSP Data
`
`No
`
`FIG. 7
`
`
`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 10 of 10
`
`US 6,804, 780 Bl
`
`800
`
`~
`
`Start
`
`Receive a Downloadable ~
`
`81 0
`
`Fetch Downloadable vJ
`
`Components
`
`8 20
`
`Include Fetched Components in vJ
`
`The Downloadable
`
`8 30
`
`Perform a Hashing Function on
`the Downloadable to Generate
`a Downloadable 10
`
`8 40
`
`8 50
`
`Store the Downloadable I D ~
`
`End
`
`FIG. 8
`
`
`
`US 6,804,780 Bl
`
`1
`SYSTEM AND METHOD FOR PROTECTING
`A COMPUTER AND A NETWORK FROM
`HOSTILE DOWNLOADABLES
`
`PRIORITY REFERENCE TO RELATED
`APPLICATION
`This application is a continuation of and hereby incorpo(cid:173)
`rates by reference U.S. patent application Ser. No. 08/964,
`388, entitled "System and Method for Protecting a Com(cid:173)
`puter and a Network from Hostile Downloadables," filed
`Nov. 6, 1997, which is now U.S. Pat. No. 6,092,194, which
`claims priority to provisional application Serial No. 60/030,
`639, entitled "System and Method for Protecting a Com(cid:173)
`puter from Hostile Downloadables," filed on Nov. 8, 1996,
`by inventor Shlomo Touboul.
`
`INCORPORATION BY REFERENCE TO
`RELATED APPLICATIONS
`This application hereby incorporates by reference related
`U.S. patent application Ser. No. 08/790,097, entitled "Sys(cid:173)
`tem and Method for Protecting a Client from Hostile
`Downloadables," filed on Jan. 29, 1997, which is now U.S.
`Pat. No. 6,167,520, by inventor Shlomo Touboul; and
`hereby incorporates by reference provisional application
`Ser. No. 60/030,639, entitled "System and Method for
`Protecting a Computer from Hostile Downloadables," filed
`on Nov. 8, 1996, by inventor Shlomo Touboul.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates generally to computer networks,
`and more particularly provides a system and method for
`protecting a computer and a network from hostile Down(cid:173)
`loadables.
`2. Description of the Background Art
`The Internet is currently a collection of over 100,000
`individual computer networks owned by governments,
`universities, nonprofit groups and companies, and is expand(cid:173)
`ing at an accelerating rate. Because the Internet is public, the
`Internet has become a major source of many system dam(cid:173)
`aging and system fatal application programs, commonly
`referred to as "viruses."
`Accordingly, programmers continue to design computer
`and computer network security systems for blocking these
`viruses from attacking both individual and network com- 45
`puters. On the most part, these security systems have been
`relatively successful. However, these security systems are
`not configured to recognize computer viruses which have
`been attached to or configured as Downloadable application
`programs, commonly referred to as "Downloadables." A 50
`Downloadable is an executable application program, which
`is downloaded from a source computer and run on the
`destination computer. Downloadable is typically requested
`by an ongoing process such as by an Internet browser or web
`engine. Examples of Downloadables include Java™ applets 55
`designed for use in the Java™ distributing environment
`developed by Sun Microsystems, Inc., JavaScript scripts
`also developed by Sun Microsystems, Inc., ActiveX™ con(cid:173)
`trols designed for use in the ActiveX™ distributing envi(cid:173)
`ronment developed by the Microsoft Corporation, and 60
`Visual Basic also developed by the Microsoft Corporation.
`Therefore, a system and method are needed to protect a
`network from hostile Downloadables.
`
`2
`prises a security policy, an interface for rece1vmg a
`Downloadable, and a comparator, coupled to the interface,
`for applying the security policy to the Downloadable to
`determine if the security policy has been violated. The
`5 Downloadable may include a Java™ applet, an ActiveX™
`control, a JavaScript™ script, or a Visual Basic script. The
`security policy may include a default security policy to be
`applied regardless of the client to whom the Downloadable
`is addressed, a specific security policy to be applied based on
`10 the client or the group to which the client belongs, or a
`specific policy to be applied based on the client/group and on
`the particular Downloadable received. The system uses an
`ID generator to compute a Downloadable ID identifying the
`Downloadable, preferably, by fetching all components of the
`15 Downloadable and performing a hashing function on the
`Downloadable including the fetched components.
`Further, the security policy may indicate several tests to
`perform, including (1) a comparison with known hostile and
`non-hostile Downloadables; (2) a comparison with Down-
`20 loadables to be blocked or allowed per administrative over(cid:173)
`ride; (3) a comparison of the Downloadable security profile
`data against access control lists; ( 4) a comparison of a
`certificate embodied in the Downloadable against trusted
`certificates; and (5) a comparison of the URL from which the
`25 Downloadable originated against trusted and untrusted
`URLs. Based on these tests, a logical engine can determine
`whether to allow or block the Downloadable.
`The present invention further provides a method for
`protecting a computer from suspicious Downloadables. The
`30 method comprises the steps of receiving a Downloadable,
`comparing the Downloadable against a security policy to
`determine if the security policy has been violated, and
`discarding the Downloadable if the security policy has been
`violated.
`It will be appreciated that the system and method of the
`present invention may provide computer protection from
`known hostile Downloadables. The system and method of
`the present invention may identify Downloadables that
`40 perform operations deemed suspicious. The system and
`method of the present invention may examine the Down(cid:173)
`loadable code to determine whether the code contains any
`suspicious operations, and thus may allow or block the
`Downloadable accordingly.
`
`35
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram illustrating a network system,
`in accordance with the present invention;
`FIG. 2 is a block diagram illustrating details of the
`internal network security system of FIG. 1;
`FIG. 3 is a block diagram illustrating details of the
`security program and the security database of FIG. 2;
`FIG. 4 is a block diagram illustrating details of the
`security policies of FIG. 3;
`FIG. 5 is a block diagram illustrating details of the
`security management console of FIG. 1;
`FIG. 6Ais a flowchart illustrating a method of examining
`for suspicious Downloadables, in accordance with the
`present invention;
`FIG. 6B is a flowchart illustrating details of the step for
`finding the appropriate security policy of FIG. 6A;
`FIG. 6C is a flowchart illustrating a method for determin(cid:173)
`ing whether an incoming Downloadable is to be deemed
`65 suspicious;
`FIG. 7 is a flowchart illustrating details of the FIG. 6 step
`of decomposing a Downloadable; and
`
`SUMMARY OF THE INVENTION
`The present invention provides a system for protecting a
`network from suspicious Downloadables. The system com-
`
`
`
`US 6,804,780 Bl
`
`3
`FIG. 8 is a flowchart illustrating a method 800 for
`generating a Downloadable ID for identifying a Download(cid:173)
`able.
`
`DETAILED DESCRIPTION OF 1HE
`PREFERRED EMBODIMENT
`
`4
`examination of incoming Downloadables, and also may be
`stored in data storage device 230 and loaded into RAM 235
`(as illustrated) for execution by CPU 205.
`FIG. 3 is a block diagram illustrating details of the
`5 security program 255 and the security database 240. The
`security program 255 includes an ID generator 315, a policy
`finder 317 coupled to the ID generator 315, and a first
`comparator 320 coupled to the policy finder 317. The first
`comparator 320 is coupled to a logical engine 333 via four
`10 separate paths, namely, via Path 1, via Path 2, via Path 3 and
`via Path 4. Path 1 includes a direct connection from the first
`comparator 320 to the logical engine 333. Path 2 includes a
`code scanner coupled to the first comparator 320, and an
`Access Control List (ACL) comparator 330 coupling the
`15 code scanner 325 to the logical engine 333. Path 3 includes
`a certificate scanner 340 coupled to the first comparator 320,
`and a certificate comparator 345 coupling the certificate
`scanner 340 to the logical engine 333. Path 4 includes a
`Uniform Resource Locator (URL) comparator 350 coupling
`20 the first comparator 320 to the logical engine 3330. A
`record-keeping engine 335 is coupled between the logical
`engine 333 and the event log 245.
`The security program 255 operates in conjunction with
`the security database 240, which includes security policies
`305, known Downloadables 307, known Certificates 309
`and Downloadable Security Profile (DSP) data 310 corre-
`sponding to the known Downloadables 307. Security poli(cid:173)
`cies 305 includes policies specific to particular users 260 and
`default (or generic) policies for determining whether to
`allow or block an incoming Downloadable. These security
`policies 305 may identify specific Downloadables to block,
`specific Downloadables to allow, or necessary criteria for
`allowing an unknown Downloadable. Referring to FIG. 4,
`security policies 305 include policy selectors 405, access
`35 control lists 410, trusted certificate lists 415, URL rule bases
`420, and lists 425 of Downloadables to allow or to block per
`administrative override.
`Known Downloadables 307 include lists of Download(cid:173)
`abies which Original Equipment Manufacturers (OEMs)
`40 know to be hostile, of Downloadables which OEMs know to
`be non-hostile, and of Downloadables previously received
`by this security program 255. DSP data 310 includes the list
`of all potentially hostile or suspicious computer operations
`that may be attempted by each known Downloadable 307,
`45 and may also include the respective arguments of these
`operations. An identified argument of an operation is
`referred to as "resolved." An unidentified argument is
`referred to as "unresolved." DSP data 310 is described below
`with reference to the code scanner 325.
`The ID generator 315 receives a Downloadable (including
`the URL from which it came and the use riD of the intended
`recipient) from the external computer network 105 via the
`external communications interface 210, and generates a
`Downloadable ID for identifying each Downloadable. The
`Downloadable ID preferably includes a digital hash of the
`complete Downloadable code. The ID generator 315 pref-
`erably prefetches all components embodied in or identified
`by the code for Downloadable ID generation. For example,
`the ID generator 315 may prefetch all classes embodied in
`or identified by the Java™ applet bytecode to generate the
`Downloadable ID. Similarly, the ID generator 315 may
`retrieve all components listed in the INF file for an
`ActiveX™ control to compute a Downloadable ID.
`Accordingly, the Downloadable ID for the Downloadable
`65 will be the same each time the ID generator 315 receives the
`same Downloadable. The ID generator 315 adds the gener(cid:173)
`ated Downloadable ID to the list of known Downloadables
`
`FIG. 1 is a block diagram illustrating a network system
`100, in accordance with the present invention. The network
`system 100 includes an external computer network 105,
`such as the Wide Area Network (WAN) commonly referred
`to as the Internet, coupled via a communications channel
`125 to an internal network security system 110. The network
`system 100 further includes an internal computer network
`115, such as a corporate Local Area Network (LAN),
`coupled via a communications channel 130 to the internal
`network computer system 110 and coupled via a communi(cid:173)
`cations channel135 to a security management console 120.
`The internal network security system 110 examines
`Downloadables received from external computer network
`105, and prevents Downloadables deemed suspicious from
`reaching the internal computer network 115. It will be
`further appreciated that a Downloadable is deemed suspi(cid:173)
`cious if it performs or may perform any undesirable
`operation, or if it threatens or may threaten the integrity of 25
`an internal computer network 115 component. It is to be
`understood that the term "suspicious" includes hostile,
`potentially hostile, undesirable, potentially undesirable, etc.
`Security management console 120 enables viewing, modi(cid:173)
`fication and configuration of the internal network security 30
`system 110.
`FIG. 2 is a block diagram illustrating details of the
`internal network security system 110, which includes a
`Central Processing Unit (CPU) 205, such as an Intel Pen(cid:173)
`tium® microprocessor or a Motorola Power PC®
`microprocessor, coupled to a signal bus 220. The internal
`network security system 110 further includes an external
`communications interface 210 coupled between the com(cid:173)
`munications channel125 and the signal bus 220 for receiv(cid:173)
`ing Downloadables from external computer network 105,
`and an internal communications interface 225 coupled
`between the signal bus 220 and the communications channel
`130 for forwarding Downloadables not deemed suspicious
`to the internal computer network 115. The external commu(cid:173)
`nications interface 210 and the internal communications
`interface 225 may be functional components of an integral
`communications interface (not shown) for both receiving
`Downloadables from the external computer network 105 and
`forwarding Downloadables to the internal computer network
`115.
`Internal network security system 110 further includes
`Input/Output (110) interfaces 215 (such as a keyboard,
`mouse and Cathode Ray Tube (CRT) display), a data storage
`device 230 such as a magnetic disk, and a Random-Access
`Memory (RAM) 235, each coupled to the signal bus 220. 55
`The data storage device 230 stores a security database 240,
`which includes security information for determining
`whether a received Downloadable is to be deemed suspi(cid:173)
`cious. The data storage device 230 further stores a users list
`260 identifying the users within the internal computer net- 60
`work 115 who may receive Downloadables, and an event log
`245 which includes determination results for each Down(cid:173)
`loadable examined and runtime indications of the internal
`network security system 110. An operating system 250
`controls processing by CPU 205, and is typically stored in
`data storage device 230 and loaded into RAM 235 (as
`illustrated) for execution. A security program 255 controls
`
`50
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`
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`US 6,804,780 Bl
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`5
`307 (if it is not already listed). The ID generator 315 then
`forwards the Downloadable and Downloadable ID to the
`policy finder 317.
`The policy finder 317 uses the use riD of the intended user
`and the Downloadable ID to select the specific security 5
`policy 305 that shall be applied on the received Download(cid:173)
`able. If there is a specific policy 305 that was defined for the
`user (or for one of its super groups) and the Downloadable,
`then the policy is selected. Otherwise the generic policy 305
`that was defined for the user (or for one of its super groups) 10
`is selected. The policy finder 317 then sends the policy to the
`first comparator 320.
`The first comparator 320 receives the Downloadable, the
`Downloadable ID and the security policy 305 from the
`policy finder 317. The first comparator 320 examines the
`security policy 305 to determine which steps are needed for
`allowing the Downloadable. For example, the security
`policy 305 may indicate that, in order to allow this
`Downloadable, it must pass all four paths, Path 1, Path 2,
`Path 3 and Path 4. Alternatively, the security policy 305 may
`indicate that to allow the Downloadable, the it must pass 20
`only one of the paths. The first comparator 320 responds by
`forwarding the proper information to the paths identified by
`the security policy 305.
`
`15
`
`25
`
`30
`
`35
`
`Path 1
`In path 1, the first comparator 320 checks the policy
`selector 405 of the security policy 305 that was received
`from the policy finder 317. If the policy selector 405 is either
`"Allowed" or "Blocked," then the first comparator 320
`forwards this result directly to the logical engine 333.
`Otherwise, the first comparator 320 invokes the comparisons
`in path2 and/or path 3 and/or path 4 based on the contents
`of policy selector 405. It will be appreciated that the first
`comparator 320 itself compares the Downloadable ID
`against the lists of Downloadables to allow or block per
`administrative override 425. That is, the system security
`administrator can define specific Downloadables as
`"Allowed" or "Blocked."
`Alternatively, the logical engine 333 may receive the
`results of each of the paths and based on the policy selector 40
`405 may institute the final determination whether to allow or
`block the Downloadable. The first comparator 320 informs
`the logical engine 333 of the results of its comparison.
`
`6
`An Example List of Operations Deemed Potentially
`Hostile
`
`File operations: READ a file, WRITE a file;
`Network operations: LISTEN on a socket, CONNECT to
`a socket, SEND data, RECEIVE data, VIEW INTRA(cid:173)
`NET;
`Registry operations: READ a registry item, WRITE a
`registry item;
`Operating system operations: EXIT WINDOWS, EXIT
`BROWSER, START PROCESS/THREAD, KILL
`PROCESS/THREAD, CHANGE PROCESS/
`THREAD PRIORITY, DYNAMICALLY LOAD A
`CLASS/LIBRARY, etc.; and
`Resource usage thresholds: memory, CPU, graphics, etc.
`In the preferred embodiment, the code scanner 325 performs
`a full-content inspection. However, for improved speed but
`reduced security, the code scanner 325 may examine only a
`portion of the Downloadable such as the Downloadable
`header. The code scanner 325 then stores the DSP data into
`DSP data 310 (corresponding to its Downloadable ID), and
`sends the Downloadable, the DSP data to the ACL com(cid:173)
`parator 330 for comparison with the security policy 305.
`The ACL comparator 330 receives the Downloadable, the
`corresponding DSP data and the security policy 305 from the
`code scanner 325, and compares the DSP data against the
`security policy 305. That is, the ACL comparator 330
`compares the DSP data of the received Downloadable
`against the access control lists 410 in the received security
`policy 305. The access control list 410 contains criteria
`indicating whether to pass or fail the Downloadable. For
`example, an access control list may indicate that the Down(cid:173)
`loadable fails if the DSP data includes a WRITE command
`to a system file. The ACL comparator 330 sends its results
`to the logical engine 333.
`
`Path 3
`
`In path 3, the certificate scanner 340 determines whether
`the received Downloadable was signed by a certificate
`authority, such as VeriSign, Inc., and scans for a certificate
`embodied in the Downloadable. The certificate scanner 340
`forwards the found certificate to the certificate comparator
`345. The certificate comparator 345 retrieves known certifi-
`45 cates 309 that were deemed trustworthy by the security
`administrator and compares the found certificate with the
`known certificates 309 to determine whether the Download(cid:173)
`able was signed by a trusted certificate. The certificate
`comparator 345 sends the results to the logical engine 333.
`
`Path 2
`In path 2, the first comparator 320 delivers the
`Downloadable, the Downloadable ID and the security policy
`305 to the code scanner 325. If the DSP data 310 of the
`received Downloadable is known, the code scanner 325
`retrieves and forwards the information to the ACL compara- 50
`tor 330. Otherwise, the code scanner 325 resolves the DSP
`data 310. That is, the code scanner 325 uses conventional
`parsing techniques to decompose the code (including all
`prefetched components) of the Downloadable into the DSP
`data 310. DSP data 310 includes the list of all potentially 55
`hostile or suspicious computer operations that may be
`attempted by a specific Downloadable 307, and may also
`include the respective arguments of these operations. For
`example, DSP data 310 may include a READ from a specific
`file, a SEND to an unresolved host, etc. The code scanner 60
`325 may generate the DSP data 310 as a list of all operations
`in the Downloadable code which could ever be deemed
`potentially hostile and a list of all files to be accessed by the
`Downloadable code. It will be appreciated that the code
`scanner 325 may search the code for any pattern, which is
`undesirable or suggests that the code was written by a
`hacker.
`
`Path 4
`
`In path 4, the URL comparator 350 examines the URL
`identifying the source of the Downloadable against URLs
`stored in the URL rule base 420 to determine whether the
`Downloadable comes from a trusted source. Based on the
`security policy 305, the URL comparator 350 may deem the
`Downloadable suspicious if the Downloadable comes from
`an untrustworthy source or if the Downloadable did not
`come from a trusted source. For example, if the Download(cid:173)
`able comes from a known hacker, then the Downloadable
`may be deemed suspicious and presumed hostile. The URL
`comparator 350 sends its results to the logical engine 333.
`The logical engine 333 examines the results of each of the
`paths and the policy selector 405 in the security policy 305
`65 to determine whether to allow or block the Downloadable.
`The policy selector 405 includes a logical expression of the
`results received from each of the paths. For example, the
`
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`logical engine 333 may block a Downloadable if it fails any
`one of the paths, i.e., if the Downloadable is known hostile
`(Path 1), if the Downloadable may request suspicious opera(cid:173)
`tions (Path 2), if the Downloadable was not signed by a
`trusted certificate authority (Path 3), or if the Downloadable 5
`did came from an untrustworthy source (Path 4). The logical
`engine 333 may apply other logical expressions according to
`the policy selector 405 embodied in the security policy 305.
`If the policy selector 405 indicates that the Downloadable
`may pass, then the logical engine 333 passes the Download-
`able to its intended recipient. Otherwise, if the policy
`selector 405 indicates that the Downloadable should be
`blocked, then the logical engine 333 forwards a non-hostile
`Downloadable to the intended recipient to inform the user
`that internal network security system 110 discarded the 15
`original Downloadable. Further, the logical engine 333
`forwards a status report to the record-keeping engine 335,
`which stores the reports in event log 245 in the data storage
`device 230 for subsequent review, for example, by the MIS
`director.
`FIG. 5 is a block diagram illustrating details of the
`security management console 120, which includes a security
`policy editor 505 coupled to the communications channel
`135, an eve