Backdoor.Lala.C

SUMMARY

Backdoor.Lala.C is a Trojan Horse that steals confidential information from a compromised computer. It is a variant of Backdoor.Lala that installs one additional file, detected as Backdoor.Trojan, to allow for remote access. The existence of the Pntask.exe file is an indication of a possible infection.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (LiveUpdate™ Weekly) August 6, 2003
• Virus Definitions (Intelligent Updater) August 6, 2003

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
• Releases Confidential Info: Captures system information and passwords.
• Compromises Security Settings: Allows unauthorized remote access to an infected computer.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Lala runs, it does the following:

1. Copies itself as %System%Pntask.exe.
   
   NOTE: %System% is a variable. The Trojan locates the system folder and copies itself to that location. The default location is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
2. Creates the file, %System%Hnsys32.dll (11,776 bytes in size). Symantec antivirus products detect this file as Keylogger.Trojan.
   
   
3. Creates the file, %Windir%Bnlgt32.exe (46,298 bytes in size). Symantec antivirus products detect this file as Backdoor.Trojan.
   
   NOTE: %Windir% is a variable. The Trojan locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
   
   
4. Adds the value:
   
   "PNtask Services" = "%System%pntask.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the Trojan starts each time you start Windows.
   
   
5. Deletes the value:
   
   "WindowsMGM"
   
   from the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
6. Looks for the file, Winmgm32.exe, in the %Windows% and %System% directories, and deletes it if found.
   
   NOTE: This is the filename and registry key that the W32.Sobig.A@mm worm uses.
   
   
7. Launches the program, %System%Mmtask.exe, if it exists.

See the Backdoor.Lala writeup for more information about the information-stealing capabilities of this Trojan.

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

The following instructions pertain to 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: Stop the Trojan process.
3. Run a full system scan and delete all the files detected as Backdoor.Lala.C, Backdoor.Trojan, or Keylogger.Trojan.
4. Remove the value that the Trojan added to the registry.
   

For specific details on each of these procedures, read the following instructions.

1. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
  
  The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

2. Restarting the computer in Safe mode or ending the Trojan process

• Windows 95/98/Me
  Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions, 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 alphabetically sort the processes.
  5. Scroll through the list and look for mmtask.exe, pntask.exe, or bnlgt32.exe.
  6. If you find one of these files, click it, and then click End Process.
  7. Exit the Task Manager.
     

3. Scanning for and deleting the infected files

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that 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.Lala.C, Backdoor.Trojan, or Keylogger.Trojan, click Delete.

4. Removing the value added to the registry

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

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