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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.392 -- ISS Security Alert Code Blue Worm 11 September 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: "Code Blue" Worm Impact: Denial of Service Execute Arbitrary Code/Commands Access Required: Remote Ref: AA-2001.02 ESB-2000.295 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Internet Security Systems Security Alert September 10, 2001 Code Blue Worm Synopsis: ISS X-Force is tracking a new worm found in the wild named "Code Blue". Testing and analysis of this worm reveals that it is similar in functionality to the "Code Red" worm, which was released in July 2000. It is believed that the Code Blue worm will not be as effective as Code Red, but it still poses a significant threat to unpatched systems. X-Force has received preliminary reports from a limited number of users who may have detected Code Blue activity as early as September 6, 2001. Description: Code Blue is not a memory resident worm like Code Red, which makes Code Blue easier to detect. It is distributed via a single .DLL (dynamic link library) and executed by an .EXE file. However, Code Blue is similar to Code Red in its method of propagation. Once a system is infected, Code Blue will spawn approximately 100 threads, which will search for additional systems to infect. Code Blue scans "neighboring" IP addresses in an effort to reduce scans on un-routable IP networks. Code Blue will mistakenly scan 127.0.0.0 (loopback) addresses, but it includes functionality to prevent re-infection of the same system. Code Blue does not appear to be intentionally destructive or malicious. It does not delete system files or install backdoor programs on an infected system. It does, however, greatly affect system stability, reducing the performance of infected systems. The worm installs a Visual Basic Script file (d.vbs), which removes ISAPI mappings for ".ida", ".idq", and ".printer" files, and then the worm deletes the script. Presumably, these mappings are removed to block re-infection by Code Red or to prevent other attacks using Microsoft IIS ISAPI vulnerabilities. Each day between the hours of 10am and 11am GMT (6am and 7am EDT), Code Blue will trigger a packet flooding attack against the IP address of a Chinese computer security company. It is unknown how many systems have been compromised by the Code Blue worm at this time. Code Blue uses the Microsoft IIS Web Server Folder Traversal vulnerability, which was announced in October 2000. That vulnerability is described in the following X-Force Security Alert: http://xforce.iss.net/alerts/advise68.php Microsoft released patches that eliminate this vulnerability on August 15, 2000 in response to a previous vulnerability. Microsoft also included the patch in Windows 2000 Service Pack 2, and in a Windows NT 4.0 Security Rollup Package (SRP). Due to the widespread availability of this fix, it is believed that a majority of systems may have already been patched. Although Code Blue uses several different attack strings with different sets of encoded characters, Code Blue scan attempts all follow the same general format. Code Blue will issue an HTTP HEAD query to a target and inspect its response. If Code Blue identifies an IIS installation, it will send an HTTP GET request attempting to exploit the Web Server Folder Traversal vulnerability. These requests look similar to the following: GET /.. [Encoded characters] ../winnt/system32/cmd.exe?/c+dir Recommendations: ISS RealSecure Network Sensor detects Code Blue scan attempts and will trigger HTTP_DotDot, HTTP_Head and HTTP_Windows_Executable events. ISS X-Force recommends that all RealSecure Network Sensor customers closely examine these events. ISS RealSecure Server Sensor detects Code Blue scan attempts and will trigger the following events: Startup_of_important_programs, Privileged_service_called, and Logon_process_registered. ISS BlackICE products detect Code Blue scan attempts and will trigger "2002595 - IIS system32 command" and "2003001 - HTTP port probe" events. ISS Internet Scanner customers can test for this vulnerability using the IisUnicodeTranslation check that was included in XPU 4.4 (and later updated in XPU 4.8). ISS System Scanner customers can test for this vulnerability using the MS00-078 check included in XPU 1.13 (#13). Microsoft IIS administrators who have not yet installed the patch for the Web Server Folder Traversal vulnerability are encouraged to do so immediately. For Microsoft IIS 4.0: http://www.microsoft.com/ntserver/nts/downloads/critical/q269862 For Microsoft IIS 5.0: http://www.microsoft.com/windows2000/downloads/critical/q269862 Administrators may also apply the latest IIS cumulative security patch (which includes the patch for this vulnerability), available from the following Microsoft Security Bulletin: http://www.microsoft.com/technet/security/bulletin/MS01-044.asp To remove the Code Blue worm from your computer: 1. Using Regedit, find the HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun registry key. 2. Find and delete the registry entry for C:svchost.exe. 3. Delete the file C:svchost.exe. 4. Delete the file C:d.vbs, if it remains on your system. 5. Restart your computer. Additional Information: Internet Security Systems Security Alert, "Serious flaw in Microsoft IIS Unicode translation" (describing the Microsoft IIS Web Server Folder Traversal vulnerability): http://xforce.iss.net/alerts/advise68.php Microsoft Security Bulletin MS00-078, "Patch Available for 'Web Server Folder Traversal' Vulnerability": http://www.microsoft.com/technet/security/bulletin/ms00-078.asp ______ About Internet Security Systems (ISS) Internet Security Systems is a leading global provider of security management solutions for the Internet, protecting digital assets and ensuring safe and uninterrupted e-business. With its industry-leading intrusion detection and vulnerability assessment, remote managed security services, and strategic consulting and education offerings, ISS is a trusted security provider to more than 8,000 customers worldwide including 21 of the 25 largest U.S. commercial banks and the top 10 U.S. telecommunications companies. Founded in 1994, ISS is headquartered in Atlanta, GA, with additional offices throughout North America and international operations in Asia, Australia, Europe, Latin America and the Middle East. For more information, visit the Internet Security Systems web site at www.iss.net or call 888-901-7477. Copyright (c) 2001 Internet Security Systems, Inc. Permission is hereby granted for the redistribution of this Alert electronically. It is not to be edited in any way without express consent of the X-Force. If you wish to reprint the whole or any part of this Alert in any other medium excluding electronic medium, please e-mail firstname.lastname@example.org for permission. Disclaimer The information within this paper may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties with regard to this information. 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