W95.Padania

SUMMARY

This virus infects Windows PE executable files. When an infected file is executed, the virus loads itself into memory. Then, the virus infects EXE files that are accessed or executed. In some cases, the virus overwrites some data in the file. These bytes cannot be restored.

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
• Modifies Files: Windows PE.EXE files

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

The virus modifies the PE header to load its viral code directly into upper Windows memory instead of where normal applications are loaded. When it infects a file, it either changes the entry point of the program to point to its viral code, or it inserts an instruction within the original program to jump to the viral code at the end of the file. So the virus may not be executed immediately at the start of the program even though an infected program is run.

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 repair infected files, boot to a clean DOS or Windows Startup floppy disk. Then, run Norton AntiVirus to scan and repair all files infected with W95.Padania.