This virus, is similar to many other Microsoft Word macro viruses. When executed, it first changes the following Microsoft Word options:
It disables MacroVirusProtection. This prevents the warning message from being displayed when you open a Word document that contains a macro.
It sets the option ConfirmConversions to equal False.
It attempts to hide itself by changing options so that it is not possible to view the source code of the virus inside Microsoft Word.
Next, it copies itself to the global template, Normal.dot, and to the currently active document. The replication is accomplished by exporting the entire macro module as a file, and then importing this exported file to files to be infected. The file name can be either C:\BenchFrm or C:\Bench. After the replication is finished, the virus removes the previously inserted file.
Once infected, if you click Tools, point to Macro, and then click Visual Basic Editor (or press Alt+F11), the following message appears:
"This program has performed an illegal operation and will shut down."
When you click OK, Microsoft Word is shut down.
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.
To repair infected files:
Run LiveUpdate to make sure that you have the most recent virus definitions.
Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
If any files are detected as infected by W97M.Wrench.H, click Repair.
(Optional) Re-enable Microsoft Word MacroVirusProtection. To do this, click Tools, click Options, and then click the General tab. (The exact steps may vary depending your version of Word.)
