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» ESB-2001.313 -- CERT Advisory CA-2001-22 -- W32/Sirc...
ESB-2001.313 -- CERT Advisory CA-2001-22 -- W32/Sircam Malicious Code
26 July 2001
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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.313 -- CERT Advisory CA-2001-22 W32/Sircam Malicious Code 26 July 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Outlook Outlook Express Vendor: Microsoft Operating System: Windows Impact: Execute Arbitrary Code/Commands Denial of Service Access Confidential Data Access Required: Remote Ref: ESB-2001.303 AL-2001.12 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- 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:WINDOWSTEMP) 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_USERSoftwareMicrosoftWindowsCurrentVersionExp lorerShell FoldersCache HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExp lorerShell FoldersDesktop 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]RecycledSirC32.EXE 2. appends "@ winRecycledSirC32.exe" to AUTOEXEC.BAT If the share contains a Windows folder, it also 3. copies \[share]Windows undll32.exe to \[share]Windows un32.exe 4. copies itself to \[share]Windows undll32.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 + RecycledSirC32.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_USERSoftwareMicrosoftWindowsCurrentVersionExplor erShell FoldersStartup (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_MACHINESoftwareMicrosoftWindowsCurrentVersionRunSe rvicesDriver32 is set to %SYSTEM%SCam32.exe so that W32/Sircam will run automatically at system startup. 3. The registry entry HKEY_CLASSES_ROOTexefileshellopencommand is set to "C:RecycledSirC32.exe" "%1" %*", causing W32/Sircam to execute whenever another executable is run. 4. A new registry entry, HKEY_LOCAL_MACHINESoftwareSirCam, 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_USERSoftwareMicrosoftWindowsCurrentVersi onExplorerShell FoldersPersonal HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersi onExplorerShell FoldersDesktop While the personal folder may vary with configuration, it is often set to My Documents or WindowsProfiles\%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:Recycledsircam.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://email@example.com 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: firstname.lastname@example.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 email@example.com. 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 - -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 5.0i for non-commercial use Charset: noconv iQCVAwUBO18P/QYcfu8gsZJZAQH2XAP/dFPRLX4MGRYxKSc67J+hRclhijxGIFn+ Jo7M4jWb2GeImjxdzRO5bbqGHUfV7Jm7gjXRdIdBTJuK0xIN2tdGjdp3/kEbaWE7 oqise1azNitAWSn2pEaVXidHyY3wm3ed5XHKZmShU/5PXGoa/avhnXqRrv7p/yup hBWgsoeBiLI= =WuU+ - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to firstname.lastname@example.org and we will forward your request to the appropriate person. This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: email@example.com Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBO1/3nih9+71yA2DNAQGoZgP7B5uExJOZclsv5pyQLlozUzwZfFyqkY4s oovNA3bRZFxdO84o1w4vGWDYdZ/2RRNw0jeYT9YLMK4tJd06xgq06YTqHOE7CwZA SMmvJ8HAoA2EznfQYk03re9OmmYvDTe1/OwV4eoH2tWtVSoSYaG+2AtDCuwk72Kp wHDIyIXN8Lg= =HJ4K -----END PGP SIGNATURE-----
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