`
`United States Patent
`[19]
`[11] Patent Number:
`6,092,194
`
`Touboul
`[45] Date of Patent:
`*Jul. 18, 2000
`
`[54]
`
`SYSTEM AND METHOD FOR PROTECTING
`A COMPUTER AND A NETWORK FROM
`
`5,864,683
`5,892,904
`
`1/1999 Boebert el al.
`4/1999 Atkinson et a1.
`
`
`. 395/200.79
`.
`.................. 395/187.01
`
`HOSTILE DOWNLOADABLES
`
`OTHER PUBLICATIONS
`
`Inventor: Shlomo Touboul, Kefar—Haim, Israel
`[75]
`[73] Assignee: Finjan Software, Ltd., Netanya, Israel
`
`[*] Notice;
`
`Th1s patent issued on a continued pros.
`ecution application filed under 37 CFR
`153((1), and 15 subjcct t0 the, twcuty year
`ngatxztsrm provrsions 0f 35 US“
`
`.
`[21] Appl. No" 08/964’388
`[22]
`Filed:
`Nov. 6, I997
`
`http://iel.ihs.com:80/cgi—bin/ieli
`page:
`Web
`cgi?se...2ehts%26ViewTemplate%3ddocvie%51b%2ehts,
`Okamato, E. et al., “IDiBased 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.
`(List continued on next page.)
`Primary Examiner—Robert W. Beausoliel, Jr.
`Assistant Examiner—Christopher Revak
`Attorney, A gent, 0r Firm—Graham & James LIP
`
`[60]
`
`Related U.S. Application Data
`Provisional application No. 60/030,639, Nov. 8, 1996.
`7
`
`[51]
`
`........................................................ H04L 1/00
`
`Int. Cl.
`‘
`[52] US CL ““““““““““““““““““““““““““““““““““ 713/200
`[58] Field of Search ............................... 395/18701, 186;
`713/200, 201, 202; 714/38, 704; 709/229
`
`[56]
`
`References Cited
`
`Us' PATENT DOCUMENTS
`
`5,077,677 12/1991 Murphy et a1. """"""""""""""" 395/10
`5,361,359
`11/1994 Tajalli et a1. ................. 395/700
`5,485,409
`1/1996 Gupta et a].
`395/186
`5,485,575
`1/1996 chess et a1.
`395/18314
`
`5,572,643
`11/1996 Judson
`395/793
`
`5,023,000
`4/1997 Ji et a1.
`395/18701
`..
`
`5,638,446
`6/1997 Rubin
`.. 380/25
`
`5,692,047
`11/1997 McManis
`380/4
`
`11/1997 Holden 91 a1.
`-
`395/187-01
`5,692,124
`
`2/1998 Deo .................................. 395/186
`5,720,033
`3/1998 Chang El ”L ~~~~~~~~~~~~~~ 380/25
`5,724,425
`5,740,248
`4/1998 Fieres et al.
`.. 380/25
`395/200.53
`5,761,421
`6/1998 van Hoff et al.
`
`711/203
`5,765,205
`6/1998 Breslau et a1.
`
`7/1998 Devarakonda et a1.
`5,784,459
`380/4
`
`95/200,54
`......
`5,796,952
`8/1998 Davis et a].
`..
`.. 395/20032
`5,805,829
`9/1998 Cohen et a1.
`
`.. 395/187.01
`5,832,208
`11/1998 Chen etal.
`
`........
`.. 395/75003
`5,850,559
`12/1998 Angelo et a1.
`
`[57]
`
`ABSTRACT
`
`,
`,
`A system protects a computer from suspictous Download-
`ables. The system comprises a security policy, an interface
`for receiving a Downloadable, and a comparator, coupled to
`the interface, for applying the security policy to the Down-
`loadable to determine if the security policy has been Vio-
`lated. The Downloadable may include a JavaTM applet, an
`ActiveXTM control, a JavaScriptT]VI 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, or a specific security policy to
`be applied based on the client or the group to which the
`client belongs. The system uses an ID generator to compute
`a Downloadeble .113
`Identlfymg 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 Download-
`ables; (2) a comparison With Downloadables to be blocked
`or allowed per administrative override, (3) a comparison of
`the Downloadable security profile data against access con-
`trol lists; (4) a comparison of a certificate embodied in the
`Downloadable against trusted certificates; and (5) a com-
`parison of the URI. from which the Downloadable origi-
`nated against trusted and untrusted URLs. Based on these
`tests, a logical engine can determine whether to allow or
`block the Downloadable.
`
`68 Claims, 10 Drawmg Sheets
`
`[355/
`,_/
`
`f
`
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`Send suesuuie //
`1mm User
`55,
`,
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`/_/
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0001
`
`
`
`
`
`semi/Findngs
`ELF]
`
`‘
`]
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0001
`
`
`
`6,092,194
`Page 2
`
`OTHER PUBLICATIONS
`
`“Finjan Announces a Personal Java TM Firewall For Web
`Browsers—the SurfinShieldTM 1.6”, Press Release of Finj an
`Releases SurfinShield, Oct. 21, 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 Software, Ltd., Jul. 29,
`1996, 1 page.
`“Powerful PC Security for the New World of JavaTM and
`Downloadables, Surfm ShieldTM”Artiele published on the
`Internet by Finjan Software Ltd, 1996, 2 Pages.
`“Company Profile Finjan7Safe Surfing, The Java Security
`Solutions Provider” Article published on the Internet by
`lt'injan Software Ltd, Oct. 31, 1996, 3 pages.
`“Finjan Announces Major Power Boost and New Features
`for SurfinShieldTM 2.0” Las Vegas Convention Center/Pa-
`villion 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 Consultant” Article pub-
`lished on the Internet, Home Page, Inc. 1996, 4 pages.
`Jim R. Omura, “Novel Applications of Cryptography in
`Digital Communications”, IEEE Communications Maga-
`zine, p 27, May 1990.
`Norvin Leach et al, “IE 3.0 applets will earn certification”,
`PC Week, v13, n29, p1(2), Jul. 1996.
`Microsoft Authenticode Technology, “Ensuring Account—
`ability and Authenticity for Software Components on the
`Internet”, Microsoft Corporation, Oct. 1996.
`Frequently Asked Questions About Authenticode, Microsoft
`Corporation, l’eb. 1997.
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0002
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0002
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 1 0f 10
`
`6,092,194
`
`100
`
`(J
`
`105
`
`
`External Computer Network
`
`Internal Network
`
`Security System
`
`
`
`
`
`115
`
`Internal Computer Network
`
`120
`
` Security
`
`
`
`
`Management
`Console
`
`FIG. 1
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0003
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0003
`
`
`
`CNN
`
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`
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`
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`
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`
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`9%@8850
`
`
`@92058mm.
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 2 0f 10
`
`6,092,194
`
`N.OE
`
`omN
`mmN
`
`
`
`
`>Esomm
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`
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`
`SOPHOS
`EXHIBIT 1015 - PAGE 0004
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0004
`
`
`
`
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 3 0f 10
`
`6,092,194
`
`com,
`
`2532:an"wsofiamzwcoz_mmm_____
`
`__
`
`.863
`
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`SOPHOS
`EXHIBIT 1015 - PAGE 0005
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0005
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 4 0f 10
`
`6,092,194
`
`Security Policies
`
`305
`
`/
`
`
`
`405
`
`Policy Selectors
`
`Access Control
`Lists
`
`410
`
`415
`
` Trusted
`Certificate Lists
`
`
`
`
`
`
`
`
`
`
`
`420
`
`425
`
`URL Rule Bases
`
`Lists of Downloadables
`
`to Allow or Block per
`Administrative Override
`
`FIG. 4
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0006
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0006
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 5 0f 10
`
`6,092,194
`
`120
`
`To/From
`
`Internal Computer
`Network
`
`135
`
`
`
`510
`
`.
`
`
`
`:efiur'téd.t
`r
`Analysts
`
`
`0 Icy
`IO
`Engine
`
`Event Log
`
`
`
`515
`
`User
`
`Notification
`
`
`
`
`
`Engine
`
`FIG. 5
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0007
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0007
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 6 0f 10
`
`6,092,194
`
`600
`
`R
`
`614
`
`Receive Downloadable
`
`602
`
`604
`
`Generate Downloadable ID
`
`606
`
`Find Security Policy
`
`
`
`Downloadable
`allowed?
`
`
`No
`
`
`
`Downloadable
`blocked?
`
`
`No
`
`608
`
`Yes
`
`610
`
`Yes
`
`
`
`620
`
`
`URL
`
`comparison
`
`required?
`
`ACL
`
`comparison
`
`
`required?
`
`TCL
`No
`
`
`comparison
`required?
`
`
`No
`
`616
`
`Compare U RL
`
`61 8
`
`No
`
`Yes
`
`Previously
`
`decomposed
`’?
`
`
`No
`
`Decompose Downloadable
`into DSP data
`
`
`_
`Compare DSP wath ACL
`
`
`
`630
`
`FIG. 6A
`
`
`
`
`Compare Certificate
`with TCL
`
`612
`
`624
`
`Send results to
`Logical Engine
`
`End
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0008
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0008
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 7 0f 10
`
`6,092,194
`
`606
`
`Security policy defined
`for User-ID and
`DownloadabIe?
`
`
`
`
`
`Fetch the poIicy
`
`Fetch the generic
`for
`
`security policy for
`User ID and
`
`
`
`User ID
`Downloadable
`
`
`
`FIG. BB
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0009
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0009
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 8 0f 10
`
`6,092,194
`
`
`
`655
`
`/
`
`
`Receive Results from First
`
`
`Comparator. ACL
`Comparator, Certificate
`Comparator and URL
`Comparator
`
`
`
`
`662
`
`
`
`
`Compare Results with
`Security Polrcres
`
`664
`
`Security Policies
`Confirm Pass?
`
`
`
`
`
`Send Substitute
`Downloadble to
`Inform The User
`
`Record Findings
`
`FlG. 60
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0010
`
`
`
`670
`
`
`Yes
`
`
`Pass Downloadable
`
`
`Stop Downloadable
`
`672
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0010
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 9 0f 10
`
`6,092,194
`
`628
`
`H
`
`Disassemble the Machine
`
`Code
`
`705
`
`710
`
`Resolve a Respective
`Command in The Code
`
`715
`
` Is The Resolved
`No
`Command Suspect?
`
`
`
`
`
`
`
`
`Decode and Register The
`Command and The
`
`
`Command Parameters as
`
`DSP Data
`
`
`No
`
`725
`
`Yes
`
`End
`
`FIG. 7
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0011
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0011
`
`
`
`US. Patent
`
`Jul. 18, 2000
`
`Sheet 10 0f 10
`
`6,092,194
`
`800
`
`/
`
`Receive a Downloadable
`
`Fetch Downloadable
`
`Components
`
`
`Include Fetched Components in
`The Downloadable
`
` 810
`
`
`
`
`
`
`
`
`
`820
`
`830
`
`840
`
`850
`
`Perform a Hashing Function on
`the Downloadable to Generate
`
`a Downloadable ID
`
`
`
`Store the Downloadable ID
`
`FIG. 8
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0012
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0012
`
`
`
`6,092,194
`
`1
`SYSTEM AND METHOD FOR PROTECTING
`A COMPUTER AND A NETWORK FROM
`HOSTILE DOW’NLOADABLES
`
`INCORPORATION BY REFERENCE TO
`RELATED APPLICATION
`
`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,” filed on Jan. 29, 1997, by inventor Shlomo
`Touboul.
`
`PRIORITY REFERENCE TO PROVISIONAL
`APPLICATION
`
`This application claims benefit of 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-
`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-
`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 configured to recognize computer viruses which have
`been attached to or configured as Downloadable application
`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 JavaTM 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.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a system for protecting a
`network from suspicious Downloadables. The system coni-
`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 JavaScriptTM script, or a Visual Basic script. The
`
`5
`
`10
`
`tom
`
`30
`
`L»LA
`
`40
`
`50
`
`60
`
`2
`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
`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 rises 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 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
`Downloadable originated against
`trusted and untrusted
`URLs. Based on these tests, a logical engine can determine
`whether to allow or block the Downloadable.
`
`invention further provides a method for
`The present
`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 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-
`ing whether an incoming Downloadable is to be deemed
`suspicious;
`FIG. 7 is a flowchart illustrating details of the FIG. 6 step
`of decomposing a Downloadable; and
`FIG. 8 is a flowchart
`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
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0013
`
`SOPHOS
`EXHIBIT 1015 - PAGE 0013
`
`
`
`6,092,194
`
`3
`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-
`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-
`fication and configuration 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 (l/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
`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
`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
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`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
`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
`the first comparator 320 to the logical eng'ne 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—
`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
`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-
`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 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 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 identified
`by the code for Downloadable ID generation. For example,
`the ID generator 315 may prefetch all classes embodied in
`or identified by the JavaTM applet bytecode to generate the
`Downloadable ID. Similarly,
`the ID generator 315 may
`retrieve all components listed in the .INF file 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
`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 userID of the intended user
`and the Downloadable ID to select the specific security
`policy 305 that shall be applied on the received Download-
`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
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`that was defined for the user (or for one of its super groups)
`is selected. The policy finder 317 then sends the policy to the
`first oomparator 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, it must pass only
`one of the paths. The first comparator 320 responds by
`forwarding the proper information to the paths identified by
`the security policy 305.
`Path 1
`the first comparator 320 checks the policy
`In path 1,
`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 path 2 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
`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
`Path 2
`the first comparator 320 delivers the
`In path 2,
`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 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
`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.
`An Example List of Operations Deemed Potentially IIostile
`File operations: READ a file, WRITE a file;
`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
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`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
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`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 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-
`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-
`L» .n
`, able was signed by a
`trusted certificate. The certificate
`comparator 345 sends the results to the logical engine 333.
`Path 4
`ln 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
`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 certificate authority (Path 3), or if the Downloadable
`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
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`internal network security system 110 discarded the
`that
`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 notification 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 security policy editor 505 uses an I/O interface
`similar to I/O interface 215 for enabling authorized user
`modification of the security policies 305. That is, the secu—
`rity policy editor 505 enables the authorized user to modify
`specific security policies 305 corresponding to the users 260,
`the default or generic security policy 305, the Download—
`ables to block per administrative override, the Download-
`ables to allow per administrative override, the trusted cer-
`tificate lists 415, the policy selectors 405, the access control
`lists 410, the URLs in the URL rule bases 420, etc. For
`example,
`if the authorized user learns of a new hostile
`Downloadable, then the user can add the Downloadable to
`the Downloadables to block per system override.
`The event log analysis engin