(12)
`
`United States Patent
`Touboul
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,804,780 B1
`*Oct. 12, 2004
`
`US006804780B1
`
`(54) SYSTEM AND METHOD FOR PROTECTING
`A COMPUTER AND A NETWORK FROM
`HOSTILE DOWNLOADABLES
`
`.
`_
`-
`(75) Inventor. Shlomo Touboul, Kefar harm (IL)
`
`.
`.
`.
`(73) Ass1gnee: FlIlJaIl Software, Ltd., Netanya (IL)
`( * ) Notice:
`Subject to any disclaimer, the term of this
`fljatsenct $533186?) (21f adjusted under 35
`
`.
`
`.
`
`.
`
`y
`
`ays.
`
`5,572,643 A 11/1996 Judson
`5,579,509 A * 11/1996 Furtney et al. ............. .. 703/27
`5,606,668 A
`2/1997 Shwed
`5,623,600 A
`4/1997 Jr et al.
`5,638,446 A
`6/1997 Rubin
`5,692,047 A 11/1997 McManis
`
`5,692,124 A 11/1997 H 1d
`t
`1.
`5,720,033 A
`2/1998 D20 en 6 a
`2
`$225 :6 :11:
`5:761:421 A
`6/1998 van Hoff et al.
`(List continued on neXt page.)
`
`This patent is subject to a terminal dis-
`
`FOREIGN PATENT DOCUMENTS
`
`l '
`.
`C almer
`
`(21) A 1 N 09/539 667
`pp .
`o.:
`,
`
`(22) Filed:
`
`Mar. 30, 2000
`
`Related US. Application Data
`
`(63) Continuation of application No. 08/964,388, ?led on Nov. 6,
`1997 now Pat. No. 6 092 194.
`.’
`.
`.
`. ’
`’
`60
`N .8
`P
`l
`l
`t
`N.60030639 ?ld
`(
`)
`1§§V61_S1°na app 10a Ion
`0
`/
`’
`’
`e on (W ’
`(51) I t C] 7
`H04L 9/00 G06F 11/30
`. Il . (52) US. Cl.
`
`
`
`; .......................... .. . 713/181; 713/201; 713/176;
`717/178
`(58) Field of Search .............. ............... .. 7153/200, 201,
`713/176’ 181’ 709/223’ 2271’721267é 212795;
`/
`_
`
`
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,077,677 A 12/1991 Murphy et al.
`5,359,659 A 10/1994 Rosenthal
`5,361,359 A 11/1994 Tajalli et al.
`5,485,409 A
`1/1996 Gupta et al.
`5,485,575 A
`1/1996 Chess et al.
`
`EP
`
`EP
`
`1091276 A1 * 4/2001
`
`........... .. G06F/1/00
`
`1132796 A1 * 9/2001
`OTHER PUBLICATIONS
`
`.... .. G06F/1/00
`
`Khare, “Microsoft Authenticode Analyzed” Jul. 22, 1996,
`Xent.com/FoRK—archive/summer96/0338.html, p. 1—2.*
`
`(List Continued on next page‘)
`.
`.
`.
`Primary Examzner—AyaZ Shelkh
`Assistant Examiner—Christopher Revak
`(74) Attorney, Agent, or Firm—Squire, Sanders &
`Dempsey,
`ABSTRACT
`(57)
`A computepbased method for generating a Downloadable
`ID to identify a DoWnloadable, including obtaining a DoWn
`loadable that includes one or more references to softWare
`components required by the DoWnloadable, fetching at least
`one softWare component identi?ed by the one or more
`references, and performing a function on the DoWnloadable
`and the fetched softWare components to generate a DoWn
`loadable ID. A system and a computer-readable storage
`medium are also described and claimed.
`
`18 Claims, 10 Drawing Sheets
`
`800
`
`/
`
`Receive a Downloadable
`
`Fetch Downloadable
`Components
`
`Include Fetched Components m
`The Downloadable
`
`Perform a Hashing Function on
`lhe Downloadable to Generate
`61 Downloadable ID
`
`Store the Downloadable ID
`
`820
`
`830
`
`840
`
`850
`
`

`
`US 6,804,780 B1
`Page 2
`
`US. PATENT DOCUMENTS
`
`6/1998 Breslau et al.
`5,765,205 A
`7/1998 Devarakonda et al.
`5,784,459 A
`8/1998 Davis et al.
`5,796,952 A
`9/1998 Cohen et al.
`5,805,829 A
`5,832,208 A 11/1998 Chen et al.
`5,832,274 A * 11/1998 Cutler et al. .............. .. 717/171
`5,850,559 A 12/1998 Angelo et al.
`5,859,966 A
`1/1999 Hayman et al.
`5,864,683 A
`1/1999 Boebert et al.
`5,892,904 A
`4/1999 Atkinson et al.
`5,951,698 A
`9/1999 Chen et al.
`5,956,481 A
`9/1999 Walsh et al.
`5,974,549 A 10/1999 Golan
`5,978,484 A * 11/1999 Apperson et al. ........... .. 705/54
`5,983,348 A 11/1999 11
`6,092,194 A * 7/2000 Touboul ................... .. 713/200
`6,154,844 A * 11/2000 Touboul et al. .
`713/201
`6,339,829 B1 * 1/2002 Beadle et al. ............. .. 713/201
`
`OTHER 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. ?les, 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
`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:
`
`Norvin Leach et al, “IE 3.0 Applets Will Earn Certi?cation”,
`PC Week, vol. 13, No. 29, Jul. 22, 1996, 2 pages.
`“Finjan SoftWare Releases Sur?nBoard, 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 JavaTM and
`DoWnloadables, Sur?n ShieldTM” Article published on the
`Internet by Finjan SoftWare Ltd., 1996, 2 Pages.
`Microsoft® Authenticode Technology, “Ensuring Account
`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 JavaTM FireWall For Web
`BroWsers—the Sur?nShieldTM 1.6 (formerly knoWn as Surf
`inBoard)”, Press Release of Finjan Releases Sur?nShield
`1.6, Oct. 21, 1996, 2 pages.
`Company Pro?le “Finjan—Safe Sur?ng, 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 Sur?nShieldTM 2.0” Las Vegas Convention Center/Pa
`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/authcode/signfaq.asp#9, pp. 1—13.
`Zhang, X.N., “Secure Code Distribution”, IEEE/IEE Elec
`tronic Library online, Computer, vol. 30, Issue 6, Jun., 1997,
`pp. 76—79.
`
`* cited by examiner
`
`http://iel.ihs.com:80/cgi—bin/ielicgi?se
`
`.
`
`.
`
`.
`
`2ehts%26VieWTemplate%3ddocvieW%5fb%2ehts.
`IBM AntiVirus User’s Guide Version 2.4, International
`Business Machines Corporation, Nov. 15, 1995, pp. 6—7.
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 1 0f 10
`
`US 6,804,780 B1
`
`100
`
`105
`
`External Computer Network
`
`"
`
`110
`
`Internal Network /
`Security System
`
`130
`/_/
`
`115
`
`Internal Computer Network
`
`135
`
`120
`
`Security /
`Management
`Console
`
`FIG. 1
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 2 of 10
`
`US 6,804,780 B1
`
`0:
`
`EP_n_
`
`\\.Q:£0502
`
`
`
`_m.SqEoo_mEmzxm
`
`omm
`
`mmmomm
`
`SNEmmom
`
`
`
`wmomt2EO:mco__.moE:EEooDuo
`
`momtmE_
`
`_mE9xm
`
`N.O_n_
`
`m
`
`mm
`
`omm
`
`s_<m
`
`9:580
`
`Em_.w>m
`
`Sm
`
`Q8
`
`i”
`
`93mEw>m
`
`Emma
`
`8.
`
`
`
`_mSaEoo_mE9xm
`
`m:V8262
`
`
`
`mmmaoumEma
`
`mo_>mn_
`
`bcsomw
`
`mmmnfimo
`
`mco:moE:EEoo
`
`momtwt:
`
`_mC._®uC_
`
`Patent Owner Finjan, Inc. - Ex. 2028, p. 4
`
`
`
`
`
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 3 of 10
`
`US 6,804,780 B1
`
`
`Commwmnmumobcsomm
`\.\._momSmM__
`
`__
`
`
`
`.m9moEtm0:.SOCv._
`
`
`
`wm_nmvmo_EsooEsocx
`
`mom
`
`ESm
`
`
`
`wm_o__on_bczomw
`
`___
`
`m._nmcmo_Esoo_9m_maEoo$ccmow
`
`
`
`
` mzofiamzmcoz“mmm._o<mvooomm_____
`
`___
`
`mvm
`
`_1IIIIIIIIIIIIIIIIIIIIIII1II1IIIII11I1IIIIIIIIII|IIII11IIIIII_Sm_mmm__9m_mQEoo_E:
`
`mo._
`
`.asmo_“_
`
`
`
`%_9m_maEooEccmomh9§_Eoemostmo
`
`
`_2m_maEoo_2m_wcw0
`
`EE9
`
`#5
`
`d_Em:
`
`umzmomm
`
`m_nmumo_EsoQ
`
`Patent Owner Finjan, Inc. - Ex. 2028, p. 5
`
`
`
`
`
`
`

`
`U.S. Patent
`
`0a. 12, 2004
`
`Sheet 4 0f 10
`
`US 6,804,780 B1
`
`Security Policies
`305
`
`Policy Selectors
`
`Access Control
`Lists
`
`Trusted
`Certificate Lists
`
`405
`
`410
`
`415
`
`URL Rule Bases
`
`fwm
`Std L A
`wmm d?avc
`
`wmo
`00m D r:
`Oun
`SAN
`sre d
`msmw
`to
`
`| e
`
`420
`
`/
`,/
`
`FIG. 4
`
`

`
`U.S. Patent
`
`0a. 12, 2004
`
`Sheet 5 0f 10
`
`US 6,804,780 B1
`
`120
`
`To/From
`Internal Computer
`Network
`
`135
`
`A
`
`505
`/~/
`
`510
`v H
`
`Security
`.
`.
`Policy Editor
`
`Event Log
`Analysts
`.
`Engine
`
`515
`‘ H
`
`User
`Notification
`Engine
`
`FIG. 5
`
`

`
`U.S. Patent
`
`Oct. 12,2004
`
`Sheet 6 0f 10
`
`US 6,804,780 B1
`
`600
`
`602 @ Receive Downioadable
`ms
`
`l
`l Generate Downioadable ID
`
`604
`
`Find Security Policy
`
`Downloadable
`ailowed?
`
`Downloadable
`blocked’?
`
`ACL
`comparison
`required?
`
`Previously
`decomposed
`
`614
`
`616
`
`URL
`comparison
`required?
`
`No
`
`Decompose Downioadabie
`into DSP data
`
`:
`V
`4 Compare DSP with ACL
`
`630
`
`FIG. 6A
`
`620
`
`comparison
`required?
`
`Scan Certificate
`
`l
`
`Compare Certificate
`with TCL
`/
`624
`
`, /
`Send results to
`Engine
`Logical
`
`@
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 7 0f 10
`
`US 6,804,780 B1
`
`606
`
`/
`
`Security policy defined
`for User-ID and
`Downloadable?
`
`7
`
`Fetch the generic
`security policy for
`User ID
`
`V
`
`Fetch the policy
`fer
`User ID and
`Dovvnloadable
`
`FIG. 6B
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 8 0f 10
`
`US 6,804,780 B1
`
`(
`
`Start
`
`)
`
`Receive Results from First
`660
`Comparator, ACL ?/
`Comparator, Certi?cate
`Comparator and URL
`Comparator
`
`662
`Compare Results with //
`Security Policies
`
`Security Policies
`Confirm Pass?
`
`664
`
`NO
`
`666
`
`655
`
`/—/
`
`670
`
`Pass Downloadable
`
`Stop Downloadable
`
`V
`
`672
`Send Substitute /
`Downloadbie to
`l
`f
`Th U
`n orm e ser
`
`v
`
`668
`
`Record Findings //
`
`End
`
`FIG. 6C
`
`

`
`U.S. Patent
`
`Oct. 12, 2004
`
`Sheet 9 0f 10
`
`US 6,804,780 B1
`
`628
`
`,?/
`
`(
`
`Start
`
`)
`
`"
`
`705
`
`Disassemble the Machine /
`Code
`
`T
`710
`‘Y
`Resolve a Respective /
`Command in The Code
`
`715
`
`Is The Resolved
`Command Suspect?
`
`720
`Decode and Register The
`Command and The /
`Command Parameters as
`DSP Data
`
`FIG. 7
`
`

`
`U.S. Patent
`
`0a. 12, 2004
`
`Sheet 10 0f 10
`
`US 6,804,780 B1
`
`800
`
`/
`
`810
`
`v
`
`Receive a Downioadable
`
`V
`
`Fetch Downioadable
`Components
`
`7
`
`include Fetched Components in
`The Downloadable
`
`7
`
`Perform a Hashing Function on
`the Downloadable to Generate
`a Downloadable ID
`
`7
`
`Store the Downioadable ID
`
`End
`
`FIG. 8
`
`

`
`US 6,804,780 B1
`
`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
`rates by reference US. patent application Ser. No. 08/964,
`388, entitled “System and Method for Protecting a Com
`puter and a NetWork from Hostile DoWnloadables,” ?led
`Nov. 6, 1997, Which is now US. Pat. No. 6,092,194, Which
`claims priority to provisional application Serial No. 60/030,
`639, entitled “System and Method for Protecting a Com
`puter from Hostile DoWnloadables,” ?led on Nov. 8, 1996,
`by inventor Shlomo Touboul.
`
`INCORPORATION BY REFERENCE TO
`RELATED APPLICATIONS
`This application hereby incorporates by reference related
`US. patent application Ser. No. 08/790,097, entitled “Sys
`tem and Method for Protecting a Client from Hostile
`DoWnloadables,” ?led on Jan. 29, 1997, Which is now US.
`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,” ?led
`on Nov. 8, 1996, by inventor Shlomo Touboul.
`
`10
`
`15
`
`20
`
`25
`
`2
`prises a security policy, an interface for receiving 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
`DoWnloadable may include a JavaTM applet, an ActiveXTM
`control, a J avaScriptTM 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 speci?c security policy to be applied based on
`the client or the group to Which the client belongs, or a
`speci?c 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
`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
`loadables to be blocked or alloWed per administrative over
`ride; (3) a comparison of the DoWnloadable security pro?le
`data against access control lists; (4) a comparison of a
`certi?cate embodied in the DoWnloadable against trusted
`certi?cates; and (5) a comparison of the URL from Which the
`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
`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
`perform operations deemed suspicious. The system and
`method of the present invention may examine the DoWn
`loadable code to determine Whether the code contains any
`suspicious operations, and thus may alloW or block the
`DoWnloadable accordingly.
`
`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. 6A is a ?oWchart illustrating a method of examining
`for suspicious DoWnloadables, in accordance With the
`present invention;
`FIG. 6B is a ?oWchart illustrating details of the step for
`?nding the appropriate security policy of FIG. 6A;
`FIG. 6C is a ?oWchart illustrating a method for determin
`ing Whether an incoming DoWnloadable is to be deemed
`suspicious;
`FIG. 7 is a ?oWchart illustrating details of the FIG. 6 step
`of decomposing a DoWnloadable; and
`
`30
`
`35
`
`40
`
`45
`
`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
`loadables.
`2. Description of the Background Art
`The Internet is currently a collection of over 100,000
`individual computer netWorks oWned by governments,
`universities, nonpro?t groups and companies, and is expand
`ing at an accelerating rate. Because the Internet is public, the
`Internet has become a major source of many system dam
`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
`puters. On the most part, these security systems have been
`relatively successful. HoWever, these security systems are
`not con?gured to recogniZe computer viruses Which have
`been attached to or con?gured as DoWnloadable application
`50
`programs, commonly referred to as “DoWnloadables.” A
`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 J avaTM applets
`designed for use in the JavaTM distributing environment
`developed by Sun Microsystems, Inc., JavaScript scripts
`also developed by Sun Microsystems, Inc., ActiveXTM con
`trols designed for use in the ActiveXTM distributing envi
`ronment developed by the Microsoft Corporation, and
`Visual Basic also developed by the Microsoft Corporation.
`Therefore, a system and method are needed to protect a
`netWork from hostile DoWnloadables.
`
`55
`
`60
`
`SUMMARY OF THE INVENTION
`The present invention provides a system for protecting a
`netWork from suspicious DoWnloadables. The system com
`
`65
`
`

`
`US 6,804,780 B1
`
`3
`FIG. 8 is a ?owchart illustrating a method 800 for
`generating a Downloadable ID for identifying a Download
`able.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`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
`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
`cations channel 135 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
`cious if it performs or may perform any undesirable
`operation, or if it threatens or may threaten the integrity of
`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
`?cation and con?guration of the internal network security
`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
`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
`munications channel 125 and the signal bus 220 for receiv
`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
`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 (I/O) 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.
`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
`cious. The data storage device 230 further stores a users list
`260 identifying the users within the internal computer net
`work 115 who may receive Downloadables, and an event log
`245 which includes determination results for each Down
`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
`
`10
`
`15
`
`25
`
`35
`
`40
`
`45
`
`55
`
`65
`
`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
`security program 255 and the security database 240. The
`security program 255 includes an ID generator 315, a policy
`?nder 317 coupled to the ID generator 315, and a ?rst
`comparator 320 coupled to the policy ?nder 317. The ?rst
`comparator 320 is coupled to a logical engine 333 via four
`separate paths, namely, via Path 1, via Path 2, via Path 3 and
`via Path 4. Path 1 includes a direct connection from the ?rst
`comparator 320 to the logical engine 333. Path 2 includes a
`code scanner coupled to the ?rst comparator 320, and an
`Access Control List (ACL) comparator 330 coupling the
`code scanner 325 to the logical engine 333. Path 3 includes
`a certi?cate scanner 340 coupled to the ?rst comparator 320,
`and a certi?cate comparator 345 coupling the certi?cate
`scanner 340 to the logical engine 333. Path 4 includes a
`Uniform Resource Locator (URL) comparator 350 coupling
`the ?rst 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 Certi?cates 309
`and Downloadable Security Pro?le (DSP) data 310 corre
`sponding to the known Downloadables 307. Security poli
`cies 305 includes policies speci?c 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 speci?c Downloadables to block,
`speci?c Downloadables to allow, or necessary criteria for
`allowing an unknown Downloadable. Referring to FIG. 4,
`security policies 305 include policy selectors 405, access
`control lists 410, trusted certi?cate 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
`ables which Original Equipment Manufacturers (OEMs)
`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,
`and may also include the respective arguments of these
`operations. An identi?ed argument of an operation is
`referred to as “resolved.” An unidenti?ed 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 userID 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 identi?ed
`by the code for Downloadable ID generation. For example,
`the ID generator 315 may prefetch all classes embodied in
`or identi?ed by the J avaTM applet bytecode to generate the
`Downloadable ID. Similarly, the ID generator 315 may
`retrieve all components listed in the INF ?le for an
`ActiveXTM control to compute a Downloadable ID.
`Accordingly, the Downloadable ID for the Downloadable
`will be the same each time the ID generator 315 receives the
`same Downloadable. The ID generator 315 adds the gener
`ated Downloadable ID to the list of known Downloadables
`
`

`
`US 6,804,780 B1
`
`5
`307 (if it is not already listed). The ID generator 315 then
`forwards the Downloadable and Downloadable ID to the
`policy ?nder 317.
`The policy ?nder 317 uses the userID of the intended user
`and the Downloadable ID to select the speci?c security
`policy 305 that shall be applied on the received Download
`able. If there is a speci?c policy 305 that was de?ned 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 de?ned for the user (or for one of its super groups)
`is selected. The policy ?nder 317 then sends the policy to the
`?rst comparator 320.
`The ?rst comparator 320 receives the Downloadable, the
`Downloadable ID and the security policy 305 from the
`policy ?nder 317. The ?rst 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
`only one of the paths. The ?rst comparator 320 responds by
`forwarding the proper information to the paths identi?ed by
`the security policy 305.
`
`Path 1
`In path 1, the ?rst comparator 320 checks the policy
`selector 405 of the security policy 305 that was received
`from the policy ?nder 317. If the policy selector 405 is either
`“Allowed” or “Blocked,” then the ?rst comparator 320
`forwards this result directly to the logical engine 333.
`Otherwise, the ?rst 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 ?rst
`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 de?ne speci?c 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
`405 may institute the ?nal determination whether to allow or
`block the Downloadable. The ?rst comparator 320 informs
`the logical engine 333 of the results of its comparison.
`Path 2
`In path 2, the ?rst 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
`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
`hostile or suspicious computer operations that may be
`attempted by a speci?c Downloadable 307, and may also
`include the respective arguments of these operations. For
`example, DSP data 310 may include a READ from a speci?c
`?le, a SEND to an unresolved host, etc. The code scanner
`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 ?les 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.
`
`25
`
`35
`
`40
`
`45
`
`55
`
`65
`
`6
`An Example List of Operations Deemed Potentially
`Hostile
`
`File operations: READ a ?le, WRITE a ?le;
`Network operations: LISTEN on a socket, CONNECT to
`a socket, SEND data, RECEIVE data, VIEW INTRA
`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
`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
`loadable fails if the DSP data includes a WRITE command
`to a system ?le. The ACL comparator 330 sends its results
`to the logical engine 333.
`
`Path 3
`
`In path 3, the certi?cate scanner 340 determines whether
`the received Downloadable was signed by a certi?cate
`authority, such as VeriSign, Inc., and scans for a certi?cate
`embodied in the Downloadable. The certi?cate scanner 340
`forwards the found certi?cate to the certi?cate comparator
`345. The certi?cate comparator 345 retrieves known certi?
`cates 309 that were deemed trustworthy by the security
`administrator and compares the found certi?cate with the
`known certi?cates 309 to determine whether the Download
`able was signed by a trusted certi?cate. The certi?cate
`comparator 345 sends the results to the logical engine 333.
`
`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
`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
`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
`
`

`
`US 6,804,780 B1
`
`7
`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
`tions (Path 2), if the DoWnloadable Was not signed by a
`trusted certi?cate authority (Path 3), or if the DoWnloadable
`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
`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 event log analysis engine 510 coupled betWeen
`communications channel 135 and a user noti?cation engine
`515, and a DoWnloadable database revieW engine 520
`coupled to the communications channel 135. The security
`management console 120 further includes computer com
`ponents similar to the computer components illustrated in
`FIG. 2.
`The secu