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W32.Witty.Worm

Risk Level 2: Low

Discovered:
March 20, 2004
Updated:
February 13, 2007 12:19:50 PM
Also Known As:
W32/Witty.worm [McAfee], WORM_WITTY.A [Trend]
Type:
Worm
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP

W32.Witty.Worm performs the following actions:
  1. Sends itself to remote machines from UDP source port 4000, pretending to be a valid ICQ packet.

  2. Exploits the ICQ parsing by ISS products vulnerability to gain unauthorized remote execution access to a machine using a buffer overflow. When doing so, the worm overwrites system memory and runs in the same security context as the ISS product being exploited.

  3. Sends itself to 20,000 randomly generated IP addresses with random destination ports and a UDP source port of 4000.

  4. Attempts to overwrite 128 sectors on one of the first eight physical hard drives, selected at random. The worm selects a random location on the hard drive and overwrites it with data from memory. If the randomly selected physical hard disk does not exist, the worm will continue.

  5. Returns to step 3.


Note: The fixed part of the UDP payload is 637 bytes. However the worm randomizes the size of the datagrams it sends, presumably in an effort to evade some IDS heuristics. The actual size of the sent datagrams is between 768 and 1280 bytes.


Symantec Clientless VPN Gateway
This worm does not affect Symantec's Clientless VPN technology.

Symantec Firewall/VPN 100/200 Appliances
Firewall component: By default, Symantec's Firewall/VPN appliance technology protects against the W32.Witty.Worm. We advise Administrators to verify that the security policy has not been modified to include UDP port 4000.

Symantec Gateway Security 5400 Series and Symantec Gateway Security v1.0
  • Antivirus component: LiveUpdate packages are not required for protection against this exploit.
  • IDS/IPS component: IDS/IPS updates are not required for protection against this exploit.
  • Full application inspection firewall component: By default, Symantec's full application inspection firewall technology protects against the W32.Witty.Worm. We advise Administrators to verify that their security policies have not been modified to allow a source port that includes UDP port 4000 inbound.

Symantec Enterprise Firewall 7.0.x and Symantec VelociRaptor 1.5
By default, Symantec's full application inspection firewall technology protects against the W32.Witty.Worm. We advise Administrators to verify that their security policies have not been modified to allow a source port that includes UDP port 4000 inbound.

Symantec ManHunt
ManHunt will alert on inbound W32.Witty.Worm packets destined for UDP ports 161 and 162 as "Suspicious SNMP traffic," and on inbound packets destined for port 53 as "DNS Malformed Data."

Symantec Client VPN v8.0 and Symantec VPN Client v7.x
Personal Firewall component: By default, Symantec's Client VPN personal firewall technology protects against the W32.Witty.Worm. We advise Administrators to verify that the Port Control setting has not been modified to include UDP port 4000.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Eric Chien
Summary| Technical Details| Removal

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