W32.Chaim

SUMMARY

W32.Chaim is a worm that spreads by sending messages using AOL Instant Messenger and opens a back door.

Protection

• Virus Definitions (LiveUpdate™ Daily) September 19, 2006
• Virus Definitions (LiveUpdate™ Weekly) September 20, 2006
• Virus Definitions (Intelligent Updater) September 19, 2006
• Virus Definitions (LiveUpdate™ Plus) September 19, 2006

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: Low
• Payload: Spreads by sending messages via AIM. May also connect the computer to an IRC bot channel.
• Compromises Security Settings: Modifies the Windows Secuity Center to lower security settings.

Distribution

• Distribution Level: Low
• Ports: TCP port 27397

TECHNICAL DETAILS

When W32.Chaim is executed, it performs the following actions:

1. Copies itself to the following location:
   
   %System% tps.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).
   
   
2. Adds the value:
   
   "Melt" = "[PATH TO EXECUTABLE]"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrent VersionShell Extensions
   
   
3. Creates the following registry subkey:
   
   HKEY_LOCAL_MACHINESystemCurrentControlSetServicesNETAPI
   
   which registers ntps.exe as a service, set to be started automatically when Windows starts up.
   
   
4. Modifies the value:
   
   "EnableDCOM" = "N"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftOle
   
   which disables DCOM.
   
   
5. Modifies the value:
   
   "restrictanonymous" = "1"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsa
   
   which prevents NULL session enumeration of the host.
   
   
6. Modifies the values:
   
   "AntiVirusDisableNotify" = "1"
   "AntiVirusOverride" = "1"
   "UpdatesDisableNotify" = "1"
   "FirewallDisableNotify" = "1"
   "FirewallOverride" = "1"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurity Center
   
   which lowers Windows security settings.
   
   
7. Modifies the value:
   
   "EnableFirewall" = "0"
   
   in the registry subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallStandardProfile
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallDomainProfile
   
   which lowers Windows security settings.
   
   
8. Modifies the value:
   
   "DoNotAllowXPSP2" = "1"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsWindowsUpdate
   
   
9. Modifies the value:
   
   "WaitToKillServiceTimeout" = "7000"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControl
   
   which decreases waiting time to kill services when Windows is shut down.
   
   
10. Modifies the value:
    
    "Start" = "4"
    
    in the registry subkeys:
    
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceswscsvc
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMessenger
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesRemoteRegistry
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTlntSvr
    
    which stops Windows services such as the Security Center, Messenger, Remote Registry, and Telnet.
    
    
11. Modifies the value:
    
    "AUOptions" = "0x00000001"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionWindowsUpdateAuto Update
    
    to disable automatic Windows update.
    
    
12. Adds the values:
    
    "AutoShareWks" = "0"
    "AutoShareServer" = "0"
    
    to the registry subkeys:
    
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceslanmanserverparameters
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceslanmanworkstationparameters
    
    which prevents administrative shares.
    
    
13. Opens a back door and connects to the following IRC network on TCP port 27397:
    
    rom.fost[REMOVED]
    
    The back door allows an attacker to perform any of the following actions:
    
    
    • Downloading and uploading files.
    • Start the replication process by sending the following message to contacts in the AOL Instant Messenger contact list:
      
      hey would it be ok if i upload this picture of you to my blog?
      
      This message contains a URL pointing to a file named image[RANDOM NUMBER].com, which is a copy of the worm.
      
      
14. Downloads the following file:
    
    [http://]www.jkoeleman.nl/media/[REMOVED]
    
    The worm saves the file as:
    
    %SystemDrive%spec.exe
    
    Note: %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.
    
    
15. Attempts to connect to the following IP address:
    
    209.123.8.[REMOVED]

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.
4. Delete any values added to the registry.
5. Restore the Windows Security Center.
   

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:
  • If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.
  • If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.
• 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 a full system scan

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, follow the instructions displayed by your antivirus program.

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.


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. 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_MACHINESOFTWAREMicrosoftWindowsCurrent VersionShell Extensions
   
   
5. In the right pane, delete the value:
   
   "Melt" = "[PATH TO EXECUTABLE]"
   
   
6. Navigate to and delete the following subkey:
   
   HKEY_LOCAL_MACHINESystemCurrentControlSetServicesNETAPI
   
   
7. Navigate to the subkeys:
   
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceslanmanserverparameters
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceslanmanworkstationparameters
   
   
8. In the right pane, delete the values:
   
   "AutoShareWks" = "0"
   "AutoShareServer" = "0"
   
   
9. Restore the following registry entries:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftOle"EnableDCOM" = "N"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsa"restrictanonymous" = "1"
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallDomainProfile"EnableFirewall" = "0"
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallStandardProfile"EnableFirewall" = "0"
   HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsWindowsUpdate"DoNotAllowXPSP2" = "1"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControl"WaitToKillServiceTimeout" = "7000"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceswscsvc"Start" = "4"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMessenger"Start" = "4"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesRemoteRegistry"Start" = "4"
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTlntSvr"Start" = "4"
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionWindowsUpdateAuto Update"AUOptions" = "0x00000001"
   
   
10. Exit the Registry Editor.

5. To restore the Windows Security Center
This risk attempts to disable the features in the Windows Security Center, available in Windows XP Service Pack 2. If you are running Windows XP Service Pack 2 and would like to restore the full functionality of the Windows Security Center, please complete the following steps:

Important: If your computer is connected to a domain, you may not be able to adjust these settings. If so, contact your network administrator for more information.

1. Click Start > Control Panel.
2. Double-click the Security Center.
3. In the right pane, click Windows Firewall. The Windows Firewall appears.
4. Select On.
5. Click OK to close the Windows Firewall.
6. In the left pane of the Security Center, select Change the way Security Center alerts me.
7. Click Alert Settings.
8. Select Alert Settings, Firewall, and Virus Protection.
9. Click OK
10. Click Automatic Updates.
11. Select Automatic.
12. Click OK.
13. Exit the Security Center.