W97M.Dotor.A@mm

SUMMARY

W97M.Dotor.A@mm is a macro virus that drops a Windows executable and disables Microsoft Word macro security. The macro virus infects when you open an infected document.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 26, 2002
• Virus Definitions (Intelligent Updater) June 25, 2002

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
• Payload: Infects Word documents on opening
• Modifies Files: Infects Word documents on opening

Distribution

• Distribution Level: High

TECHNICAL DETAILS

When W97M.Dotor.A@mm runs, it does the following:

It creates \%Windows%Doctor.exe. This file is detected as W32.Dotor.A@mm.

NOTE: %Windows% is a variable. The worm locates the Windows folder (by default this is C:Windows or C:Winnt) and copies itself to that location.

It adds the value

DocTor      \%Windows%Doctor.exe /newrun

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion

so that Doctor.exe runs when you start Windows.

The macro virus also disables Microsoft Word macro security by setting the value data of Level to 1.

in one of these registry keys:

HKEY_CURRENT_USERSoftwareMicrosoftOffice10.0WordSecurity
HKEY_CURRENT_USERSoftwareMicrosoftOffice9.0WordSecurity

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. Update the virus definitions, and run a full system scan. Repair all files that Norton AntiVirus (NAV) detects as W97M.Dotor.A@mm, and delete files that NAV detects as W32.Dotor.A@mm.
2. Delete the value
   
   DocTor
   
   from the registry key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   
3. Restore the Microsoft Word macro security settings.

For details on how to do this, read the following instructions.

To scan with Norton AntiVirus and delete or repair the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
     
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
3. Run a full system scan.
4. Delete all files that NAV detects as W32.Dotor.A@mm.
5. Repair all files that NAV detects as W97M.Dotor.A@mm.

To remove the value from the registry:

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   
4. In the right pane, delete the following value:
   
   DocTor
   
5. Click Registry, and click Exit.

To restore the Microsoft Word macro security settings:

1. Click the Tools menu.
2. Point to Macro.
3. Click Security.
4. Click the desired security level, and click OK.