W32.Semisoft.59904

SUMMARY

This virus infects Windows .exe files, including 9x and NT. The virus creates infected files on the system and attempts to infect other Windows executables. The virus attempts to ping four different IP addresses believed to be located in New Zealand. It then opens a port, allowing remote-control access. The virus also attempts to modify the registry to execute the virus on startup. There are several variants of this virus, which have been found previously in the wild.

Protection

• Virus Definitions (Intelligent Updater) February 10, 1998

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Modifies Files: Notepad.exe, Setup.exe, Win.ini, Registry.
• Causes System Instability: Due to a running task, you may experience difficulty shutting down Windows. Depending on the variant, this task may be labeled as 6.666 or 4.4.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

This virus is a prepending PE infector, which replicates under 9x and NT. The virus infects the files Notepad.exe and Setup.exe, and creates clean backups of these files as Notepadx.exe and Setupx.exe.
The virus creates the files Winipx.exe, Winipxa.exe, and Winsrvc.exe in the Windows directory.
The virus adds the following registry entries:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServicesWINIPX = C:WindowsWinipx.exe
HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsNTCurrentVersionWinlogonShell=Explorer.exe, Winipx.exe

Winipx.exe is created in the Windows Startup folder after several executions of the virus.

The virus attempts to ping four different IP addresses believed to be located in New Zealand. By pinging these machines, the virus is able to pass the IP address of the infected machine to the virus writer. Port 531 is opened, awaiting connections, allowing remote-control access.

The .B variant will copy itself as C:Testexe.exe and Winipxa.exe to the Windows directory. This variant also replaces Notepad.exe with an infected version, and backs up the clean version as Notepadx.exe. In addition to the registry changes, the virus also adds an entry to the Win.ini.

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

Repair found infections.
Delete all files created by the virus.
Restore files replaced by the virus with known clean backups.
Remove registry and Win.ini entries.