W32.Gnuman.Worm

SUMMARY

W32.Gnuman.Worm is a worm that spreads using the Gnutella network. The worm can change its own file name to match any query. However, the file size is always 8192 bytes, and it always has the extension .exe.

W32.Gnuman.Worm appears to have been written by Mandragore, a member of the virus writing group 29A.

Protection

• Virus Definitions (Intelligent Updater) February 27, 2001

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low

Distribution

• Distribution Level: Medium
• Target of Infection: The Gnutella Network

TECHNICAL DETAILS

W32.Gnuman.Worm is a proof-of-concept worm that spreads using the Gnutella network. When it is executed, it opens port 99 on the computer.

This worm is not the first worm that attempts to spread using the Gnutella network. VBS.Gnutella, discovered in May 2000, is another example of a worm that spreads using the Gnutella network. However, W32.Gnuman.Worm is more complex than the previous worms. The worm spreads by responding to queries made on clients attached to the Gnutella network. To be infected by this worm, the 8-KB executable file must be downloaded and executed.

W32.Gnuman.Worm can change its own file name to match any query. However, because the file always has the extension .exe and is always 8192 bytes in size, it is believed that it will not infect many users. W32.Gnuman.Worm is considered a proof-of-concept worm. This worm does not contain a payload.

Inside the file is the string:

freely shared by mandragore/29A

This string appears to be the signature of the author of this worm.

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

To remove this worm:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
3. Delete any files detected as W32.Gnuman.Worm.