W32.Bobax.Z@mm

SUMMARY

W32.Bobax.Z@mm is a mass-mailing worm that lowers security settings and allows a compromised computer to be used as a covert proxy. The worm also sends an email to addresses gathered from the compromised computer.

The worm propagates by exploiting the Microsoft Windows LSASS Buffer Overrun Vulnerability (described in Microsoft Security Bulletin MS04-011).

Note: W32.Bobax.Z@mm is a minor variant of W32.Bobax.N.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 3, 2005
• Virus Definitions (Intelligent Updater) June 3, 2005

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
• Payload: Modifies registry entries to lower security settings.
• Large Scale E-mailing: Creates a mass-mailing of itself.
• Degrades Performance: Creates a mass-mailing of itself, which may clog mail servers or degrade network performance.
• Compromises Security Settings: Lowers security settings by blocking access to security-related Web sites.

Distribution

• Distribution Level: High
• Subject of Email: Varies
• Name of Attachment: Varies
• Size of Attachment: 31,232 bytes
• Target of Infection: Unpatched systems vulnerable to LSASS exploit - MS04-011.

TECHNICAL DETAILS

When W32.Bobax.Z@mm is executed, it performs the following actions:

1. Creates the DLL file %Temp%[RANDOM FILE NAME].tmp.
   
   Note: %Temp% is a variable that refers to the Windows temporary folder. By default, this is C:WindowsTEMP (Windows 95/98/Me/XP) or C:WINNTTemp (Windows NT/2000).
   
   
2. Injects this .tmp file into processes with a Window class name of "Shell_TrayWnd" as a thread. The worm then ends its own process.
   
   Note: Normally, the Explorer.exe process has a Windows class name "Shell_TrayWnd".
   
   
3. May copy itself to the %System% folder using a random generated file name.
   
   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).
   
   
4. Add the following value:
   
   "[RANDOM VALUE]" = "%System%RANDOM FILE NAME.exe"
   
   to the registry subkeys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   RunServices
   
   so that the risk runs every time Windows starts.
   
   
5. Appends the following text to the Hosts file to block access to security-related Web sites:
   
   255.255.255.255
   ar.atwola.com
   atdmt.com
   avp.ch
   avp.com
   avp.ru
   awaps.net
   ca.com
   dispatch.mcafee.com
   download.mcafee.com
   download.microsoft.com
   downloads.microsoft.com
   engine.awaps.net
   f-secure.com
   ftp.f-secure.com
   ftp.sophos.com
   go.microsoft.com
   liveupdate.symantec.com
   mast.mcafee.com
   mcafee.com
   msdn.microsoft.com
   my-etrust.com
   nai.com
   networkassociates.com
   office.microsoft.com
   phx.corporate-ir.net
   secure.nai.com
   securityresponse.symantec.com
   service1.symantec.com
   sophos.com
   spd.atdmt.com
   support.microsoft.com
   symantec.com
   update.symantec.com
   updates.symantec.com
   us.mcafee.com
   vil.nai.com
   viruslist.ru
   windowsupdate.microsoft.com
   www.avp.ch
   www.avp.com
   www.avp.ru
   www.awaps.net
   www.ca.com
   www.f-secure.com
   www.kaspersky.ru
   www.mcafee.com
   www.my-etrust.com
   www.nai.com
   www.networkassociates.com
   www.sophos.com
   www.symantec.com
   www.trendmicro.com
   www.viruslist.com
   www.viruslist.ru
   www3.ca.com
   
   
6. Attempts to lower security settings by creating the following registry entries:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurityCenter"AntivirusDisableNotify" = "1"
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurityCenter"FirwallDisableNotify" = "1"
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurityCenter"FirewallOverride" = "1"
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurityCenter"UpdatesDiasbleNotify" = "1"
   
   
7. Attempts to use the compromised computer as a covert proxy.
   
   
8. Exploits the Microsoft Windows LSASS Buffer Overrun Vulnerability (described in Microsoft Security Bulletin MS04-011) in order to spread to vulnerable computers.
   
   
9. Retrieves email addresses from files with the following extensions:
   
   
   • .HTM
   • .TXT
   • .DBX
     
     
10. Retrieves email addresses from the Windows Address Book files and Windows Messenger contact list.
    
    
11. Sends an email to all addresses found. The email has the following characteristics:
    
    Subject:
    One of the following:
    
    
    • Cool
    • pics
    • funny
    • bush
    • joke
    • secret
      
      Message:
      One of the following:
      
      
    • Saddam Hussein - Attempted Escape, Shot dead
      Attached some pics that i found
    • Osama Bin Laden Captured.
      Attached some pics that i found
    • Testing
    • Secret!
    • Hey,
      Remember this?
    • Hello,
      Long time! Check this out!
    • Hey,
      I was going through my album, and look what I found..
    • Hey,
      Check this out :-)
      
      The message may also contain the following strings:
      
      
    • +++ Attachment: No Virus found
    • +++ You are protected
    • +++ [A FAKE URL]
      
      Attachment:
      One of the following:
      
      
    • Cool
    • pics
    • funny
    • bush
    • joke
    • secret
      
      with .PIF, .SCR, .EXE, or .ZIP as an extension.
      
      
12. Avoids sending itself to email addresses whose domain contains any of the following:
    
    
    • ogle
    • yaho
    • help
    • admi
    • ter@
    • micr
    • msn.
    • hotm
    • supp
    • yman
    • viru
    • tren
    • secu
    • .mil
    • urhq
    • pand
    • afee
    • soph
    • kasp
    • .gov
    • nort
      
      
13. May download the following non-viral files:
    
    
    • download.yahoo.com/dl/installs/msgr6suite.exe
    • ftp.scarlet.be/pub/mozilla.org/firefox/releases/1.0/win32/en-US/Firefox Setup 1.0.exe
    • ftp.newaol.com/aim/win95/Install_AIM.exe
    • g.msn.com/7MEEN_US/EN/SETUPDL.EXE
      

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

Removal using the W32.Bobax Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of W32.Bobax.Z@mm. Use this removal tool first, as it is the easiest way to remove this threat.

Manual 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. Remove all the entries that the risk added to the hosts file.
3. Update the virus definitions.
4. Run a full system scan and delete all the files detected.
5. Delete any values added to the registry.
6. 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 remove all the entries that the risk added to the hosts file

1. Navigate to the following location:
   
   
   • Windows 95/98/Me:
     %Windir%
   • Windows NT/2000/XP:
     %Windir%System32driversetc
     
     Notes:
   • The location of the hosts file may vary and some computers may not have this file. There may also be multiple copies of this file in different locations. If the file is not located in these folders, search your disk drives for the hosts file, and then complete the following steps for each instance found.
   • %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).
     
     
2. Double-click the hosts file.
3. If necessary, deselect the "Always use this program to open this program" check box.
4. Scroll through the list of programs and double-click Notepad.
5. When the file opens, delete all the entries added by the risk. (See the Technical Details section for a complete list of entries.)
6. Close Notepad and save your changes when prompted.
   
   

3. 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 document: 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 the document: 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.

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 your Symantec antivirus product reports that it cannot delete a detected 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.

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
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
   
   
5. In the right pane, delete the value:
   
   "[RANDOM VALUE]" = "%System%[RANDOM FILE NAME].exe"
   
6. Exit the Registry Editor.
   
   

6. 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.