Backdoor.Berbew.E

SUMMARY

Backdoor.Berbew.E is a backdoor Trojan horse that gives an attacker access to your computer. The Trojan opens TCP ports 23232 and 32121, by default.

This Trojan is packed with MPPEC.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 9, 2004
• Virus Definitions (Intelligent Updater) June 9, 2004

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: May steal passwords.
• Compromises Security Settings: Allows unauthorized access to the infected system.

Distribution

• Distribution Level: Low
• Ports: TCP ports 23232, 32121, and two other randomly selected ports.

TECHNICAL DETAILS

When Backdoor.Berbew.E is run, it does the following:

1. Creates a copy of itself as %System%<8 random characters>.exe.
   
   

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   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).

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2. Creates the file, %System%<8 random characters>.dll.
   
   
3. Creates several files in the %Temp% folder named <8 random characters>.htm. These file names are used as parameters when the Trojan accesses a predefined remote system.
   
   
4. Sets these registry keys to the following:
   
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorer
   Autocomplete"AutoSuggest" = "yes"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones1"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones2"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones3"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones4"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settingsones5"1601" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionInternet Settings"GlobalUserOffline" = "0"
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorer
   BrowseNewProcess"BrowseNewProcess = "yes"
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain"Use FormSuggest" = "yes"
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain"FormSuggest Passwords" = "yes"
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain"FormSuggest PW Ask" = "yes"
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain"Start Page" = "http: //128.121.180.88"
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain"Search Page" = "http: //128.121.180.88"
   
   
   These settings will affect a number of Microsoft Internet Explorer settings, such as the home page.
   
   
5. Runs a command shell on TCP port 23232 so that an attacker can gain access by connecting to this port.
   
   
6. Runs an FTP server on TCP port 32121 and opens two randomly selected TCP ports.
   
   
7. Allows an attacker to do any of the following:
   • Restart or shut down the infected system
   • View a list of running processes
   • Stop processes
   • View a log of system information
   • Download and execute a file from a specified Internet address
   • Steal cached passwords

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. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as Backdoor.Berbew.E.
4. Reset the Internet Explorer home page.
5. Reset the Internet Explorer search page.
6. Check other Internet Explorer settings.

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"

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

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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 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.

3. To scan for and delete 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.Berbew.E, click Delete.
   
   

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   Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix 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.
   
   When all the infected files have been deleted, restart the computer in Normal mode.
   

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4. To reset the Internet Explorer home page

1. Start Microsoft Internet Explorer.
2. Connect to the Internet, and then go to the page that you want to set as your home page.
3. Click the Tools menu > Internet Options.
4. In the Home page section of the General tab, click Use Current, and then click OK.

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article, "Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159."

5. To reset the Internet Explorer Search page
Follow the instructions for your version of Windows.

Windows 98/Me/2000

1. Start Microsoft Internet Explorer.
2. Click the Search button on the toolbar.
3. In the Search pane, click Customize.
4. Click Reset.
5. Click Autosearch Settings.
6. Select a search site from the drop-down list, and then click OK.
7. Click OK.

Windows XP
Because Windows XP is set by default to use animated characters in the search, how you do this can vary. Read all the instructions before you start.

1. Start Microsoft Internet Explorer.
2. Click the Search button on the toolbar.
3. Do one of the following:
   • If the pane that opens looks similar to this picture:
     
     
     
     
     
     click the word Customize, then skip to step h.
     
     
   • If the pane that opens has the words "Search Companion" at the top, and the center looks similar to this picture:
     
     
     
     
     
     click the "Change preferences" link as shown above. Proceed with step d.
     
     
4. Click the "Change Internet search behavior" link.
5. Under "Internet Search Behavior," click "With Classic Internet Search."
6. Click OK. Then close Internet Explorer. (Close the program for the change to take effect.)
7. Start Internet Explorer. When the search pane opens, it should now look similar to this:
   
   
   
   
   
   Click the word Customize, and then proceed with the next step.
   
   
8. In the Search pane, click Customize.
9. Click Reset.
10. Click Autosearch Settings.
11. Select a search site from the drop-down list, and then click OK.
12. Click OK.
13. Do one of the following:
    • If you were using (or want to continue using) the "Classic Internet Search" panel, stop here (or proceed with the next section).
    • If you want to go back to the "Search Companion" search (it usually has an animated character at the button), proceed with step n.
      
      
14. Click the word Customize again.
15. In the "Customize Search Settings" window, click "Use Search Companion," and then click OK.
16. Close Internet Explorer. The next time you open it, it will again use the Search Companion.

6. To check other Internet Explorer settings.
This Trojan also makes several other changes to the registry, such as Web content zones. Because these are customizable, it is not possible for us to recommend what to change these to.

In Internet Explorer, these settings are accessed from Tools > Internet Options > Security tab.

If you are not sure what to change these to, you should reset each zone to the default setting by clicking the Default button.