Backdoor.Coreflood - 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. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as Backdoor.Coreflood.
5. Reverse the changes that were made to the registry.

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"

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 restart the computer in Safe mode or VGA mode

• For Windows 95, 98, Me, 2000, or XP users, shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode. For instructions, refer to the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in VGA mode.

4. 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.Coreflood, write down the full path to and the file name of the infected file or files.
   
   Important: Do not skip this step. You will need the file names later in the removal.
   
   
4. Click Delete. If your Symantec antivirus product reports that it cannot delete an infected file, proceed to section 5 (modifying the registry), then restart the computer and manually delete the file.

5. To reverse the changes to 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 keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start > Run.
2. Type regedit
   
   Then click OK.
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Run
   
   
4. In the right pane, delete any value that refers to any files that were detected as Backdoor.Coreflood.
   
   Note: All the variants do not add an entry to this key.
   
   
5. Navigate to and select the key:
   
   HKEY_LOCAL_MACHINE/Software/Classes/CLSID
   
   
6. Click Edit > Find.
   
   
7. In the "Find what" box, type the file name of the .dll file that was detected as Backdoor.Coreflood in section 4.
   
   
8. If you find an entry of the form:
   
   "(Default)"="%System%\<detected file name>.dll
   
   in the registry key:
   
   HKEY_LOCAL_MACHINE\Software\Classes\CLSID\{<random clsid>}\InProcServer32
   
   then write down the <random clsid> value>
   
   Then, in the left pane, delete the subkey:
   
   HKEY_LOCAL_MACHINE\Software\Classes\CLSID\{<random clsid>}
   
   
9. Next, click Edit > Find to repeat the search, as there may be more than one such key. Delete any that are found.
   
   
10. Navigate to and delete the key:
    
    HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion
    \Explorer/Browser Helper Objects/{<random clsid>}
    
    where {<random clsid>} matches one of the values found and deleted in the previous searches.
    
    
11. Navigate to and delete the key:
    
    HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/
    Explorer/ShellIconOverlayIdentifiers/<detected file name>
    
    Note: <detected file name> should match the name of the infected dll file. For example, if abcdwxyz.dll was detected as Backdoor.Coreflood, then delete the registry key:
    
    HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/
    Explorer/ShellIconOverlayIdentifiers/abcdwxyz
    
    
12. Exit the Registry Editor.
    
    
13. Restart the computer. If you could not delete any files in section 4, use Windows Explorer to locate and delete them.

Technical Details