Backdoor.Wold

SUMMARY

Backdoor.Wold is a backdoor Trojan that gives an attacker unauthorized access to an infected computer. The Trojan modifies the system to execute itself at startup and additionally upon execution of ICQ. The existence of the file "Dimitris World.exe" is an indicator of a possible infection.

Protection

• Virus Definitions (LiveUpdate™ Weekly) November 4, 2002
• Virus Definitions (Intelligent Updater) October 31, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Modifies Files: Modifies the registry.
• Releases Confidential Info: Attempts to transmit login names and cached network passwords to hacker.
• Compromises Security Settings: Allows unauthorized access to the compromised machine.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Wold runs, it performs the following actions:

It copies itself as %system%Dimitris World.exe.

NOTE: %system% is a variable. The Trojan locates the System folder and copies itself to that location. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).

The Trojan creates the following values so that it starts when you start Windows:

• Ctwpf    %system%Dimitris World.exe
  
  in the registry key
  
  HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
  
• Dhtovn    %system%Dimitris World.exe
  
  in the registry key
  
  HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
  

The Trojan uses registry keys that are created by Mirabilis ICQ Agent software. If the following registry keys do not exist, the Trojan creates them:

HKEY_CURRENT_USERSoftwareMirabilis
HKEY_CURRENT_USERSoftwareMirabilisICQ
HKEY_CURRENT_USERSoftwareMirabilisICQAgent
HKEY_CURRENT_USERSoftwareMirabilisICQAgentAppsCebfz

As a result, when the ICQ software is run, the Trojan also runs.

It then creates the following values in HKEY_CURRENT_USERSoftwareMirabilisICQAgentAppsCebfz:

Enable     Yes
Parameters     [empty string]
Path     %system%DIMITRIS WORLD.EXE
Startup     %system%

If the operating system is Windows 95/98/Me, Backdoor.Wold attempts to obtain access to the password cache that is stored on the local computer. The cached passwords include modem and dial-up passwords, URL passwords, share passwords, and others.

The Trojan inventories successfully established RAS connection information to authenticate its access to the remote access server.

After Backdoor.Wold is installed, it waits for the commands from the remote client. The commands allow the hacker to perform the following actions:

• Deliver system and network information to the hacker, including login names and cached network passwords.
• Alter many system parameters, such as screen resolution and system colors.
• Enumerate and terminate processes.
• Enumerate files on the local computer.

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

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Do one of the following:
   • Windows 95/98/Me: Restart the computer in Safe mode.
   • Windows NT/2000/XP: End the Trojan process.
3. Run a full system scan, and delete all files that are detected as Backdoor.Wold.
4. Reverse the changes that the Trojan made to the registry.
   

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

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once 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 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.

To restart the computer in Safe mode or end the Trojan process:

• Windows 95/98/Me
  Restart the computer in Safe mode. All Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode.

• Windows NT/2000/XP
  To end the Trojan process:
  1. Press Ctrl+Alt+Delete once.
  2. Click Task Manager.
  3. Click the Processes tab.
  4. Double-click the Image Name column header to sort the processes alphabetically.
  5. Scroll through the list, and look for Dimitris World. Please note that only 15 characters are displayed.
  6. If you find the file, click it, and then click End Process.
  7. Exit the Task Manager.
     

To scan for and delete the infected files:

1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
   • Norton AntiVirus consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • Symantec enterprise antivirus products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
2. Run a full system scan.
3. If any files are detected as infected with Backdoor.Wold, click Delete.

To reverse the changes that the Trojan made to 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. Do one of the following:
   • If you use Mirabilis ICQ software, skip to step 4.
   • If you do not use Mirabilis ICQ software, navigate to and delete the following keys:
     
     HKEY_CURRENT_USERSoftwareMirabilis
     HKEY_CURRENT_USERSoftwareMirabilisICQ
     HKEY_CURRENT_USERSoftwareMirabilisICQAgent
     
4. Navigate to the key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
5. In the right pane, delete the value
   
   Ctwpf    %system%DIMITRIS WORLD.EXE
   
6. Navigate to the key
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
   
7. In the right pane, delete the value
   
   Dhtovn    %system%DIMITRIS WORLD.EXE
   
8. Navigate to the key
   
   HKEY_CURRENT_USERSoftwareMirabilisICQAgentAppsCebfz
   
9. In the right pane, delete the following values:
   
   Enable     Yes
   Parameters     [empty string]
   Path     %system%DIMITRIS WORLD.EXE
   Startup     %system%
   
10. Exit the Registry Editor.