W32.Denisbee

SUMMARY

W32.Denisbee is a network-aware worm that copies itself to all non-password-protected network shared folders.

Protection

• Virus Definitions (Intelligent Updater) November 3, 2000

TECHNICAL DETAILS

W32.Denisbee is a network-aware worm that copies itself as the following file names to all non-password-protected network shared folders and to the %SystemRoot%System directory on the infected computer:

• Trojan.exe
• Pager.exe
• Crack.exe
• Lines99.exe
• Worm.exe
• Draw.exe
• Mpeg.exe
• Byte.exe
• Visual.exe
• Word.exe
• Done.exe
• Horse.exe
• Express.exe
• Friday.exe
• Winapp.exe
• Netbios.exe
• Wapihlp.exe
• Msvxapp.exe
• Dsgrun.exe
• Winver32.exe
• Gk32ctrl.exe

NOTE: %SystemRoot% is a variable. The worm locates the WindowsSystem folder (by default this is C:WindowsSystem or C:WinntSystem32) and copies itself to that location.

The worm configures itself to start when Windows starts by adding the value:

Netvx = %SystemRoot%System\%WormName%

NOTE: %WormName% can be any of the names from the preceding list of file names.

to the registry key:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

It also adds the value:

DisablePwdCaching" = "1"

to the registry key:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionPoliciesNetwork

It also adds the following values:

Installed" = "%Installed Date and Time%"
User" = "%Username%"
RunCount" = "%Number of Times Worm Executed%"
MineCount" = "%Some Number Used by Worm%"
Ver" = "200002180"
InstalledAs" = "%WormName%"

to the registry key that it creates:

HKEY_LOCAL_MACHINESOFTWARETress

W32.Denisbee also stores the location of the worm as the default value in the registry key:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionApp Paths o.exe

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

Run NAV, delete all files that are detected as W32.Denisbee, and then remove and modify the values that the worm added to the registry.

To remove files that are detected as W32.Denisbee:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate. LiveUpdate 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. 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. Delete all files that are detected as W32.Denisbee.

To edit 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_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following values:
   
   Netvx   %SystemRoot%System\%WormName%
   
   NOTE: By default, %SystemRoot% is C:Windows or C:WINNT, depending on your version of Windows. If you installed Windows in a different folder, then go to that folder. %WormName% is the name that is generated by the worm and is randomly chosen from the list of names in the Technical Description.
   
5. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionPoliciesNetwork
   
6. Click Edit, point to New, click String Value, and add the following string value:
   
   DisablePwdCaching
   
7. In the right pane, right-click DisablePWdCaching, and click Modify.
8. Add the following value to the Value data field (include the quotation marks):
   
   "1"
   
9. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESOFTWARETress
   
10. Select the key, press Delete, and then click Yes at the confirmation prompt.
11. Navigate to the following key:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionApp Paths o.exe
    
12. Select the key, press Delete, and then click Yes at the confirmation prompt.
13. Click File, and click Exit.