Backdoor.Mepcod

SUMMARY

Backdoor.Mepcod is a Trojan horse that opens a back door and downloads a file containing additional commands.

Protection

• Virus Definitions (LiveUpdate™ Weekly) August 24, 2005
• Virus Definitions (Intelligent Updater) August 24, 2005

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: Medium
• Payload: Opens a back door and allows a remote attacker to have unauthorized access to the compromised computer .

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Mepcod is executed, it performs the following actions:

1. Copies itself as the following file:
   
   %Windir%systemMcAfeeScanPlus.exe.
   
   Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows or C:Winnt.
   
   
2. Drops the following file and opens it with mspaint.exe:
   
   %CurrentFolder%me.bmp
   
   Note: %CurrentFolder% is a variable that refers to the folder where the risk was originally executed.
   
   
3. Creates the following file, which is used to log account information:
   
   %Windir%winlogon9.log
   
   
4. Adds the value:
   
   "McAfeeScanPlus" = %Windir%systemMcAfeeScanPlus.exe"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the risk runs every time Windows starts.
   
   
5. Adds the value:
   
   "%Windir%McAfeeScanPlus.exe" = "%Windir%systemMcAfeeScanPlus.exe:*:Enabled:McAfeeScanPlus"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESYSTEMControlSet001ServicesSharedAccess
   ParametersFirewallPolicyStandardProfileAuthorizedApplicationsList
   
   to enable the back door functionality.
   
   
6. Attempts to download files from [http://]diji-realm.net/[REMOVED]/BN2005/LogMe.php.
   
   
7. Attempts to download additional commands from [http://]diji-realm.net/[REMOVED]/BN2005/binfo.txt.

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 Symantec antivirus products that support security risk detection.

1. Disable System Restore (Windows Me/XP).
2. Update the definitions.
3. Run a full system scan.
4. Delete any values added to the registry.
   

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

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• How to disable or enable Windows Me System Restore
• How to turn off or turn on Windows XP System Restore

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).


2. To update 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 Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. 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 Virus Definitions (Intelligent Updater).
  
  The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.
  

3. To run the scan

1. Start your Symantec antivirus program, and then run a full system scan.
   
2. If any files are detected, and depending on which software version you are using, you may see one or more of the following options:
   
   Note: This applies only to versions of Norton AntiVirus that support security risk detection. If you are running a version of Symantec AntiVirus Corporate Edition that supports security risk detection, and security risk detection has been enabled, you will only see a message box that gives the results of the scan. If you have questions in this situation, contact your network administrator.
   
   • Exclude (Not recommended): If you click this button, it will set the risk so that it is no longer detectable. That is, the antivirus program will keep the security risk on your computer and will no longer detect it to remove from your computer.
     
     
   • Ignore or Skip: This option tells the scanner to ignore the risk for this scan only. It will be detected again the next time that you run a scan.
     
     
   • Cancel: This option is new to Norton Antivirus 2005. It is used when Norton Antivirus 2005 has determined that it cannot delete a security risk. This Cancel option tells the scanner to ignore the risk for this scan only, and thus, the risk will be detected again the next time that you run a scan.
     
     To actually delete the security risk:
     • Click its file name (under the Filename column).
     • In the Item Information box that displays, write down the full path and file name.
     • Then use Windows Explorer to locate and delete the file.
       
       
   • Delete: This option will attempt to delete the detected files. In some cases, the scanner will not be able to do this.
     • If you see a message, "Delete Failed" (or similar message), manually delete the file.
     • Click the file name of the risk that is under the Filename column.
     • In the Item Information box that displays, write down the full path and file name.
     • Then use Windows Explorer to locate and delete the file.
       
       

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the risk may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: 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 subkeys only. Read the document: How to make a backup of the Windows registry.

1. Click Start > Run.
2. Type regedit
   
   Then click OK.
   
   Note: If the registry editor fails to open the risk may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.
   
   
3. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the value:
   
   "McAfeeScanPlus" = %Windir%McAfeeScanPlus.exe
   
   
5. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESYSTEMControlSet001ServicesSharedAccess
   ParametersFirewallPolicyStandardProfileAuthorizedApplicationsList
   
   
6. In the right pane, delete the value:
   
   "%Windir%McAfeeScanPlus.exe" = "%Windir%McAfeeScanPlus.exe:*:Enabled:McAfeeScanPlus"
   
   
7. Exit the Registry Editor.