W97M.Likon.A

SUMMARY

W97M.Likon.A is a macro virus that infects Microsoft Word documents and the global template Normal.dot. If the current date is on or after April 17, 2000, it attempts to modify C:Autoexec.bat to format drive A. Because of a programming error, the virus creates the file C:Autoexec (without the .bat extension).

Protection

• Virus Definitions (Intelligent Updater) October 2, 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: Low

TECHNICAL DETAILS

The virus is activated on Autoexec, AutoOpen, and DocumentChange.

When executed, it does the following:

First the virus checks whether the date is on or after April 17, 2000. If it is before this date or if a file named C:Nokill.pls exists, it does nothing. Otherwise, it creates two files, C:Start, which contains a response for the Format command, and C:Autoexec, which contains the Format a: command. Since the file does not have the .bat extension, it will never be executed.

The virus next checks for a previous infection by searching for the presence of the CloseA module. If it is not present in any open documents or templates, it exports temporary files for each module. The exports are named C:Test-0-2.bas and C:Test-0-3.bas. These files are deleted after the modules are reimported.

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

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. Repair all files that are detected as W97M.Likon.A.
5. Start Windows Explorer.
6. Click the View menu (Windows 95/98/NT) or the Tools menu (Windows Me/2000), and then click Options or Folder options.
7. Click the View tab.
8. Uncheck "Hide file extensions for known file types."
9. Do one of the following:
   • Windows 95/NT: Click "Show all files."
   • Windows 98: In the Advanced settings box, under the "Hidden files" folder, click Show all files.
   • Windows Me/2000: Uncheck "Hide protected operating system files," and under the "Hidden files" folder, click "Show hidden files and folders."
10. Click Apply, and then click OK.
11. In the left pane, select drive C.
12. In the right pane, locate and delete the Autoexec file and the Start file.
    
    CAUTION: Make sure that you delete the Autoexec file that does not have a file extension. Do not delete the Autoexec.bat file.
    
13. Delete C:Test-0-2.bas and C:Test-0-3.bas if you find them.