JS.Restarter

SUMMARY

This Trojan horse is inserted in the C:WindowsStart MenuProgramsStartUp folder as the file Winmem.hta.

Protection

• Virus Definitions (Intelligent Updater) February 5, 2001

Threat Assessment

Wild

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

Damage

• Damage Level: Low
• Payload Trigger: On system start up
• Payload: Shut down Windows

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When an infected computer is restarted, JS.Restarter immediately shuts down Windows, effectively preventing the operating system from being used.

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 Trojan, you need to restart in MS-DOS mode and then delete the Winmem.hta file from the C:WindowsStart MenuProgramsStartUp folder.

To restart in MS-DOS mode:

• Windows 95
  1. Restart the computer.
  2. When "Starting Windows 95..." appears on the screen, press F8. The Windows 95 Startup Menu appears.
  3. Select "Command Prompt only," and then press Enter.
• Windows 98
  1. Restart the computer.
  2. As the computer restarts, press and hold down the Ctrl key until the Windows 98 Startup Menu appears.
     
     NOTE: On some computers, a keyboard or other error may appear during restart as you hold down the Ctrl key. If so, then follow the prompts to press a key to continue (for example, the message may prompt you to press the Esc key), then immediately press the Ctrl key again.
     
  3. Select "Command Prompt only" and then press Enter.
     

To delete Winmem.hta:

1. At the command prompt, type the following commands, pressing Enter after each one:
   
   NOTE: If Windows is installed in a different folder, make the appropriate substitution.
   
   cd windowsstartm~1programsstartup
   del winmem.hta
   
2. Restart the computer.