Discovered: March 01, 2001
Updated: February 13, 2007 11:55:13 AM
Type: Worm
Systems Affected: Windows


W32.Taz@mm is a worm written in Visual Basic. The worm can spread using mIRC, Pirch, and Microsoft Outlook. However, to function, this worm requires the Msbvm60.dll file. This is not a standard system file, and it is therefore not likely that this worm will execute on most Windows systems.

Antivirus Protection Dates

  • Initial Rapid Release version March 01, 2001
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version March 01, 2001
  • Latest Daily Certified version September 28, 2010 revision 036

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Neal Hindocha

Discovered: March 01, 2001
Updated: February 13, 2007 11:55:13 AM
Type: Worm
Systems Affected: Windows


W32.Taz@mm is a mass-mailing worm. The worm spreads as a 92 KB executable file. The file name, the subject of the email, and the body of the email are chosen randomly. To execute, the worm requires the Msbvm60.dll file. This file is not installed with Windows; this prevents the worm from running on most systems.

When executed, this worm attempts to email everyone in the Microsoft Outlook address book. It then creates a copy of itself in the root of drive C. Finally, it attempts to locate mIRC, which is a popular client used to access the IRC network from a Windows computer.

If the worm finds mIRC, it modifies the Script.ini file. This causes an infected computer to send the worm to other users over the IRC network. The modified Script.ini file is also detected as W32.Taz@mm.

After this worm performs its malicious actions, it displays the following message:



WalruS appears to be name used by the author of W32.Taz@mm.

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: Neal Hindocha

Discovered: March 01, 2001
Updated: February 13, 2007 11:55:13 AM
Type: Worm
Systems Affected: Windows


In the unlikely event that the worm has been able to execute on the system, delete all files detected as W32.Taz@mm.

Writeup By: Neal Hindocha