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Microsoft Windows (all versions)

Week of July 25, 2001


CERT Advisory CA-2001-22 W32/Sircam Malicious Code

   Original release date: July 25, 2001
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

   * Microsoft Windows (all versions)

Overview

   'W32/Sircam' is malicious code that spreads through email and
   potentially through unprotected network shares. Once the malicious
   code has been executed on a system, it may reveal or delete sensitive
   information.

   As of 10:00EST(GMT-4) Jul 25, 2001 the CERT/CC has received reports of
   W32/Sircam from over 300 individual sites.

I. Description

   W32/Sircam can infect a machine in one of two ways:
     * When executed by opening an email attachment containing the
       malicious code
     * By copying itself into unprotected network shares

 Propagation Via Email

   The virus can appear in an email message written in either English or
   Spanish with a seemingly random subject line. All known versions of
   W32/Sircam use the following format in the body of the message:

   English 
       Hi! How are you?
       [middle line]
       See you later. Thanks
   
   Spanish
       Hola como estas ?
       [middle line]
       Nos vemos pronto, gracias.

   Where [middle line] is one of the following:

   English
       I send you this file in order to have your advice
       I hope you like the file that I sendo you
       I hope you can help me with this file that I send
       This is the file with the information you ask for

   Spanish
       Te mando este archivo para que me des tu punto de vista
       Espero te guste este archivo que te mando
       Espero me puedas ayudar con el archivo que te mando
       Este es el archivo con la informacion que me pediste

   Users who receive copies of the malicious code through electronic mail
   might recognize the sender. We encourage users to avoid opening
   attachments received through electronic mail, regardless of the
   sender's name, without prior knowledge of the origin of the file or a
   valid digital signature.

   The email message will contain an attachment whose name matches the
   subject line and has a double file extension (e.g. subject.ZIP.BAT or
   subject.DOC.EXE). The CERT/CC has confirmed reports that the first
   extension may be .DOC, .XLS, or .ZIP. Anti-virus vendors have referred
   to additional extensions, including .GIF, .JPG, .JPEG, .MPEG, .MOV,
   .MPG, .PDF, .PNG, and .PS. The second extension will be .EXE, .COM,
   .BAT, .PIF, or .LNK. The attached file contains both the malicious
   code and the contents of a file copied from an infected system.

   When the attachment is opened, the copied file is extracted to both
   the %TEMP% folder (usually C:\WINDOWS\TEMP) and the Recycled folder on
   the affected system. The original file is then opened using the
   appropriate default viewer while the infection process continues in
   the background.

   It is possible for the recipient to be tricked into opening this
   malicious attachment since the file will appear without the .EXE,
   .BAT, .COM, .LNK, or .PIF extensions if the 'Hide file extensions for
   known file types' is enabled in Windows. See IN-2000-07 for additional
   information on the exploitation of hidden file extensions.

   W32/Sircam includes its own SMTP client capabilities, which it uses to
   propagate via email. It determines its recipient list by recursively
   searching for email addresses contained in all *.wab (Windows Address
   Book) files in the %SYSTEM% folder. Additionally, it searches the
   folders referred to by

          HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Exp
          lorer\Shell Folders\Cache

          HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Exp
          lorer\Shell Folders\Desktop

   for files containing email addresses. All addresses found are stored
   in SC??.DLL or S??.DLL files hidden in the %SYSTEM% folder.

   W32/Sircam first attempts to send messages using the default email
   settings for the current user. If the default settings are not
   present, it appears to use one of the following SMTP relays:
     * prodigy.net.mx
     * NetBIOS name for 'MAIL'
     * mail. (e.g., mail.example.org)
     * dobleclick.com.mx
     * enlace.net
     * goeke.net

 Propagation Via Network Shares

   In addition to email-based propagation, analysis by anti-virus vendors
   suggests that W32/Sircam can spread through unprotected network
   shares. Unlike the email propagation method, which requires a user to
   open an attachment to infect the machine, propagation of W32/Sircam
   via network shares requires no human intervention.

   If W32/Sircam detects Windows networking shares with write access, it
    1. copies itself to \\[share]\Recycled\SirC32.EXE
    2. appends '@ win\Recycled\SirC32.exe' to AUTOEXEC.BAT

   If the share contains a Windows folder, it also
    3. copies \\[share]\Windows\rundll32.exe to
       \\[share]\Windows\run32.exe
    4. copies itself to \\[share]\Windows\rundll32.exe
    5. when virus is executed from rundll32.exe, it calls run32.exe

 Infection process

    1. When installed on a victim machine, W32/Sircam installs a copy of
       itself in two hidden files:

          + %SYSTEM%\SCam32.exe
          + Recycled\SirC32.exe

       Installing in Recycled may hide it from anti-virus software since
       some do not check this folder by default.
       Based on external analyses, there is also a probability that
       W32/Sircam will copy itself to the %SYSTEM% folder as ScMx32.exe.
       In that case, another copy is created in the folder referred to by
       HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explor
       er\Shell Folders\Startup (the current user's personal startup
       folder). The copy created in that location is named Microsoft
       Internet Office.exe. When the affected user next logs in, this
       copy of W32/Sircam will be started automatically.

    2. The registry entry
       HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunSe
       rvices\Driver32 is set to %SYSTEM%\SCam32.exe so that W32/Sircam
       will run automatically at system startup.

    3. The registry entry HKEY_CLASSES_ROOT\exefile\shell\open\command is
       set to 'C:\Recycled\SirC32.exe' '%1' %*', causing W32/Sircam to
       execute whenever another executable is run.

    4. A new registry entry, HKEY_LOCAL_MACHINE\Software\SirCam, is
       created to store data required by W32/Sircam during execution.

    5. W32/Sircam searches for filenames with .DOC, .XLS, .ZIP extensions
       in the folders referred to by

                HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersi
                on\Explorer\Shell Folders\Personal

                HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersi
                on\Explorer\Shell Folders\Desktop

       While the personal folder may vary with configuration, it is often
       set to \My Documents or \Windows\Profiles\%username%\Personal. A
       list of these files is stored in %SYSTEM%\scd.dll.

    6. W32/Sircam attaches its own binary to selected files it finds and
       stores the combined file in the Recycled folder.

II. Impact

   W32/Sircam can have a direct impact on both the computer which was
   infected as well as those with which it communicates over email.

     * Breaches of confidentiality: The malicious code will at a minimum
       search through select folders and mail potentially sensitive
       files. This form of attack is extremely serious since it is one
       from which it is impossible to recover. Once a file has been
       publicly distributed, any potentially sensitive information in it
       cannot be retracted.

     * Limit Availibility (Denial of Service)

          + Fill entire hard drive: Based on external analyses, on any
            given day, there is a probability that it will create a file
            named C:\Recycled\sircam.sys which consumes all free space on
            the C: drive. A full disk will prevent users from saving
            files to that drive, and in certain configurations impede
            system-level tasks (e.g., swapping, printing).

          + Propagation via mass emailing: W32/Sircam will attempt to
            propagate by sending itself through email to addresses
            obtained as described above. This propagation can lead to
            congestion in mail servers that may prevent them from
            functioning as expected.
            NOTE: Since W32/Sircam uses native SMTP routines connecting
            to pre-defined mail servers, propagation is independent of
            the mail client software used.

     * Loss of Integrity: Published reports indicate that on October 16
       there is a reasonable probability that W32/Sircam will attempt to
       recursively delete all files from the drive on which Windows is
       installed (typically C:).

III. Solution

 Run and Maintain an Anti-Virus Product

   It is important for users to update their anti-virus software. Most
   anti-virus software vendors have released updated information, tools,
   or virus databases to help detect and partially recover from this
   malicious code. A list of vendor-specific anti-virus information can
   be found in Appendix A.

   Many anti-virus packages support automatic updates of virus
   definitions. We recommend using these automatic updates when
   available.

 Exercise Caution When Opening Attachments

   Exercise caution when receiving email with attachments. Users should
   never open attachments from an untrusted origin, or ones that appear
   suspicious in any way. Finally, cryptographic checksums should also be
   used to validate the integrity of the file.

   The effects of this class of malicious code are activated only when
   the file in question is executed. Social engineering is typically
   employed to trick a recipient into executing the malicious file. The
   best advice with regard to malicious files is to avoid executing them
   in the first place. The following tech tip offers suggestions as to
   how to avoid them:

          Protecting yourself from Email-borne Viruses and Other
          Malicious Code During Y2K and Beyond

 Filter the Email or use a Firewall

   Sites can use email filtering techniques to delete messages containing
   subject lines known to contain the malicious code, or they can filter
   all attachments.

   Likewise, a firewall or border router can be used to stop the
   W32/Sircam outbound SMTP connections to mail servers outside of the
   local network. This filtering strategy will prevent further
   propagation of the worm from a particular host when the local mail
   configuration is not used.

Appendix A. - Vendor Information

  Aladdin Knowledge Systems

          http://www.esafe.com/home/csrt/valerts2.asp?virus_no=10068

  Central Command, Inc.

          http://support.centralcommand.com/cgi-bin/command.cfg/php/endus
          er/std_adp.php?p_refno=010718-000010

  Command Software Systems

          http://www.commandsoftware.com/virus/sircam.html

  Computer Associates

          http://www.cai.com/virusinfo/encyclopedia/descriptions/s/sircam
          137216.htm

  Data Fellows Corp

          http://www.datafellows.com/v-descs/sircam.shtml

  McAfee

          http://vil.mcafee.com/dispVirus.asp?virus_k=99141&

  Norman Data Defense Systems

          http://www.norman.com/virus_info/w32_sircam.shtml

  Panda Software

          http://www.pandasoftware.es/vernoticia.asp?noticia=987

  Proland Software

          http://www.pspl.com/virus_info/worms/sircam.htm

  Sophos

          http://www.sophos.com/virusinfo/analyses/w32sircama.html

  Symantec

          http://www.symantec.com/avcenter/venc/data/w32.sircam.worm@mm.h
          tml

  Trend Micro

          http://www.antivirus.com/vinfo/virusencyclo/default5.asp?VName=
          TROJ_SIRCAM.A

   You may wish to visit the CERT/CC's Computer Virus Resources Page
   located at: 
   
     http://www.cert.org/other_sources/viruses.html
   
   ______________________________________________________________________

   Authors: Roman Danyliw, Chad Dougherty, Allen Householder
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2001-22.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: cert@cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890
          U.S.A.

   CERT personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4)
   Monday through Friday; they are on call for emergencies during other
   hours, on U.S. holidays, and on weekends.

    Using encryption

   We strongly urge you to encrypt sensitive information sent by email.
   Our public PGP key is available from

   http://www.cert.org/CERT_PGP.key

   If you prefer to use DES, please call the CERT hotline for more
   information.

    Getting security information

   CERT publications and other security information are available from
   our web site

   http://www.cert.org/

   To subscribe to the CERT mailing list for advisories and bulletins,
   send email to majordomo@cert.org. Please include in the body of your
   message

   subscribe cert-advisory

   * 'CERT' and 'CERT Coordination Center' are registered in the U.S.
   Patent and Trademark Office.
   ______________________________________________________________________

   NO WARRANTY
   Any material furnished by Carnegie Mellon University and the Software
   Engineering Institute is furnished on an 'as is' basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed or
   implied as to any matter including, but not limited to, warranty of
   fitness for a particular purpose or merchantability, exclusivity or
   results obtained from use of the material. Carnegie Mellon University
   does not make any warranty of any kind with respect to freedom from
   patent, trademark, or copyright infringement.
     _________________________________________________________________

   Conditions for use, disclaimers, and sponsorship information

   Copyright 2001 Carnegie Mellon University.

   Revision History
   July 25, 2001: Initial release
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