W32.Varra

SUMMARY

W32.Varra is a simple Windows virus that infects .exe files. It does not have a payload.

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 16, 2003
• Virus Definitions (Intelligent Updater) July 10, 2003

TECHNICAL DETAILS

When W32.Varra is activated, it will launch the already infected host in a separate process. Then, it infects all the files on all the local hard drives.

To prevent itself from being active in more than one instance, W32.Varra will create an event that it queries for each time it is activated. Thus, if the event already exists, then it will pass control to the original host program.

W32.Varra searches for and infects all the files with the .exe extension. During its search, W32.Varra will skip a file if the name of the file begins with the following:

• RUNDLL32
• RUNONCE
• RAV
• LSASS
• SERVICES
• WINLOGON
• SPOOLSV
• MSTASK
• SCANREGW

Due to bugs in the virus, some infections will only infect the files for a limited number of generations and only on specific hard drives.

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.