W97M.ThirtyFour.A

SUMMARY

W97M.ThirtyFour.A is an encrypted macro virus that infects active documents and the Normal.dot template file.

Protection

• Virus Definitions (Intelligent Updater) May 16, 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

When an infected document is opened or closed, the macro virus performs the following actions:

1. It infects active documents and the Normal.dot template by adding the viral code. W97M.ThirtyFour.A encrypts the variable names, labels, and strings used in the macro code with a key, which is randomly generated with every infection. Also, it swaps the blocks of the code and inserts random comments and spaces to look different in every infection.
2. W97M.ThirtyFour.A changes the settings in Microsoft Word to cause the following to occur:
   • When you open a document that contains macro, the warning message no longer appears by default.
   • When you close Microsoft Word, any changes made to the Normal.dot template are automatically saved without prompting.
   • When you open a file that is not a Word document or template, the Convert File dialog box does not appear.
   • When you save a document, a backup copy will not be saved.
   • When a macro is run, Word will not display any prompts or alert messages.
   • Saving AutoRecover information will be turned off.
   • The screen updating will be turned off to speed up the macro code. You will not be able to see what the macro is doing, but it will run faster.
   • The Ctrl+Break key combination will be disabled. This will prevent you from interrupting a macro.
   • The Visual Basic Editor window will not be visible.
3. It will attempt to delete the following CommandBar Control objects:
   • Tools > Macro
   • Tools > Templates and Add-Ins...
   • Tools > Customize...
   • Tools > Options...
   • Tools > Protect Document...
   • Tools > Macros...
   • View > Toolbars
4. To make the macrocode invisible in the Visual Basic Editor window, the macro virus will change its color by creating the values
   
   CodeBackColors             1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
   CodeForeColors              1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
   
   in the registry key
   
   HKEY_CURRENT_USERSoftware
   MicrosoftVBAOffice
   
5. If the day is the 28th of any month, W97M.ThirtyFour.A will attempt to open the following Web site, using the default browser
   
   www.tendadaesperanca.com.br
   
6. If the date is March 5, the virus will display a message in Portuguese.
7. It will then create the values (the numbers 1-3 reflect infection statistics):
   
   SpockVersionNumber         <number 1>/<number 2>/<number 3>
   RegisteredOwner                  Mr. Spock <number 1>.<number 2>.<number 3>  B
   RegisteredOrganization      Copyright © 2000 Spock-Vulkan Corporation.
   
   in the registry key
   
   HKEY_LOCAL_MACHINESoftware
   MicrosoftWindowsCurrentVersion

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 virus, repair any files detected as W97M.ThirtyFour.A, undo the changes the macro virus made to the registry, and restore the Word settings.

To remove the virus:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
3. If any files are detected as W97M.ThirtyFour.A, click Repair.

To edit the registry:

CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.

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 key
   
   HKEY_CURRENT_USERSoftware
   MicrosoftVBAOffice
   
4. In the right pane, delete the values
   
   CodeBackColors
   CodeForeColors
   
5. Navigate to the key
   
   HKEY_LOCAL_MACHINESoftware
   MicrosoftWindowsCurrentVersion
   
6. In the right pane, delete the value
   
   SpockVersionNumber
   
   Then, update the values
   
   RegisteredOwner
   RegisteredOrganization
   
   by double-clicking each in turn and reentering the name of the registered owner and the registered organization of the copy of Windows that is installed on the computer.
   
7. Click OK, and then exit the Registry Editor.

To restore the Microsoft Word settings:
How you restore the default settings will vary with the version of Word. See the Microsoft Word documentation for additional information. If the virus has deleted menu items, you may have to reinstall Word.