W32.Suclove.A@mm

SUMMARY

W32.Suclove.A@mm is a mass-mailing worm that uses MS Outlook to send a copy of itself to other users. It also spreads through MIRC, and opens a back door.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 28, 2005
• Virus Definitions (Intelligent Updater) September 26, 2005

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Payload: Opens a back door that allows a remote attacker to have unauthorized access to the compromised computer.
• Large Scale E-mailing: Uses MS Outlook to send a copy of the worm to all users in the Outlook address book.
• Releases Confidential Info: Attempts to steal confidential system information.
• Degrades Performance: Creates a mass-mailing of itself, which may impact performance.

Distribution

• Distribution Level: High
• Subject of Email: Read my letter for you
• Name of Attachment: LoveLetter.doc.exe
• Size of Attachment: 126,976 bytes
• Ports: TCP port 1111

TECHNICAL DETAILS

When W32.Suclove.A@mm is executed, it performs the following actions:

1. Creates the following copies of itself:
   
   
   • %System%dllhost.dll
   • %System%LOADER32.COM
   • %Windir%LoveLetter.doc.exe
   • %SystemDrive%WINLOGON.EXE
     
     Note:
   • %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).
   • %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.
     
     
2. Adds the value:
   
   "DLL32" = "dllhost.dll"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that it runs every time Windows starts.
   
   
3. Adds the value:
   
   "@" = "%Root%WINLOGON.EXE"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   policiesExplorerRun
   
   so that it runs every time Windows starts.
   
   
4. Adds the value:
   
   "@" = ""%1" %*"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREClassesdllfileshellopencommand
   
   so that DLL files are executable.
   
   
5. Adds the value:
   
   "@" ""%System%LOADER32.COM" %1"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREClassesexefileshellopencommand
   
   so that it runs everytime an executable file is run.
   
   
6. Adds the value:
   
   "CheckedValue" = "1"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   ExplorerHideFileExt
   
   in order to hide itself from the user.
   
   
7. Adds the value:
   
   "NoFolderOptions" = "1"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   policiesExplorer
   
   in order to hide itself from the user.
   
   
8. Adds the value:
   
   "DisableRegistryTools" = "1"
   
   to the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
   PoliciesSystem
   
   in order to disable registry editing.
   
   
9. Attempts to create the file script.ini, which contains IRC script to send itself to other users, in the following folders:
   
   
   • %SystemDrive%MIRC
   • %SystemDrive%MIRC32
   • %ProgramFiles%MIRC
   • %ProgramFiles%MIRC32
     
     Note:
   • %ProgramFiles% is a variable that refers to the program files folder. By default, this is C:Program Files.
   • %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.
     
     
10. Creates and runs the file %Root%progra~1micros~1outlook.vbs. This is a VBScript file that contains code which uses MS Outlook to send a copy of the worm to all users in the Outlook address book.
    
    The email will have the following properties:
    
    Subject: Read my letter for you
    Body: this was created from the deep inside my heart.
    Attachment: LoveLetter.doc.exe
    
    
11. Creates and runs the file C:sender.vbs. This is a VBScript file that contains code to send a copy of the worm to all users found in the %Root%program filesyahoo!messengerprofiles folder.
    
    The email will have the following properties:
    
    Subject: Love, for Forgiveness :->
    Body: I love u please forgive me!...
    Attachment: LoveLetter.doc.exe
    
    
12. Opens a backdoor on TCP port 1111 that allows a remote attacker to download and execute files on the compromised 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

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. Enable registry editing. Use UnHookExe.inf tool.
4. Run a full system scan and delete all the files detected.
5. 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. Enable registry editing. Use UnHookExe.inf tool

Symantec Security Response has created a tool to reset these registry values to their default settings. WARNING: Do not use this tool unless: A Symantec technician or document directs you to do so. After reading the removal instructions in the writeup, you are sure that the tool is required. Follow these steps: 1. Download the file UnHookExec.inf and save it to your Windows desktop. (If you cannot connect to the Internet from the infected computer, download to an uninfected computer then save it to a floppy disk. Then take the floppy disk and insert it in the floppy disk drive of the infected computer.) Note: The tool has a .inf file extension. 2. Locate the download file, either on the Windows desktop or the floppy disk. 3. Right-click the UnHookExec.inf file and click install. (This is a small file. It does not display any notice or boxes when you run it.) 4. Follow any other instructions for the threat that you are trying to remove.

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, click Delete.

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 threat 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.


5. 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. For instructions refer to the document: How to make a backup of the Windows registry.

1. Click Start > Run.
2. Type regedit
3. Click OK.
   
   Note: If the registry editor fails to open the threat 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.
   
   
4. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. In the right pane, delete the value:
   
   "DLL32" = "dllhost.dll"
   
   
6. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   policiesExplorerRun
   
   
7. In the right pane, delete the value:
   
   "@" = "%Root%WINLOGON.EXE"
   
   
8. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREClassesdllfileshellopencommand
   
   
9. In the right pane, delete the value:
   
   "@" = ""%1" %*"
   
   
10. Navigate to the subkey:
    
    HKEY_LOCAL_MACHINESOFTWAREClassesexefileshellopencommand
    
    
11. In the right pane, delete the value:
    
    "@" ""%System%LOADER32.COM" %1"
    
    
12. Navigate to the subkey:
    
    HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
    policiesExplorer
    
    
13. In the right pane, reset the value to the original value if applicable:
    
    "NoFolderOptions" = "1"
    
    
14. Navigate to the subkey:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
    ExplorerHideFileExt
    
    
15. In the right pane, reset the value to the original value if applicable:
    
    "CheckedValue" = "1"
    
    
16. Navigate to the subkey:
    
    HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
    PoliciesSystem
    
    
17. In the right pane, reset the value to the original value if applicable:
    
    "DisableRegistryTools" = "1"
    
    
18. Exit the Registry Editor.