W32.Zotob.K

1. Creates the following mutex so that only one copy of the worm runs on the compromised computer at one time:
   
   wintnl.exe
   
   
2. Copies itself as the following file:
   
   %System%\wintnl.exe
   
   Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
   
   
3. Adds the value:
   
   "wintnl.exe" = "wintnl.exe"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   so that it runs every time Windows starts.
   
   
4. May fail to operate correctly if it detects it is not connected to a network or if the computer's IP address is non-routable.
   
   
5. Connects to the following IRC server on TCP port 6664 to listen for IRC commands:
   
   66.252.12.254
   
   
6. Allows the attacker to use IRC commands to perform the following actions:
   
   
   • Download and execute files from the IRC server.
   • Delete the worm from the compromised computer.
     
     
7. Opens UDP port 69 for TFTP.
   
   
8. Sends packets to randomly generated IP addresses, based on the IP address of the compromised computer. The generated IP addresses then use the first 2 octets of the compromised computer and randomly generates values for the third and fourth octets. The worm will begin to generate entirely random IP addresses after 32 failures on local IP addresses or after 512 failures, if it was successful at least once.
   
   
9. Attempts to exploit the Microsoft Windows Plug and Play Buffer Overflow Vulnerability (as described in Microsoft Security Bulletin MS05-039) on TCP port 445.
   
   
10. If successful, the exploit code will open a back door using TCP Port 8172 on the remote computer.
    
    
11. Sends the file %Temp%\[NUMBER].bat to the target computer via the back door. This file contains a TFTP script that will download a copy of the worm from the compromised computer.
    
    Note:
    • [NUMBER] represents several random numbers from 0 - 9.
    • %Temp% is a variable that refers to the Windows temporary folder. By default, this is C:\Windows\TEMP (Windows 95/98/Me/XP) or C:\WINNT\Temp (Windows NT/2000).
      
      
12. Saves the file as %Windir%\a[NUMBER].exe on the target computer and executes it.
    
    Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.
    
    
13. Ends the following processes:
    
    
    • botzor.exe
    • csm.exe
    • per.exe
    • wpa.exe
    • winpnp.exe
    • pnpsrv.exe
    • llsrv.exe
    • mousebm.exe
    • service32.exe
    • system32.exe
    • svnlitup32.exe
    • HPSV.exe
    • ssl.exe
    • upnp.exe
    • wintbp.exe
    • wintbpx.exe
    • wintnpx.exe
    • winrvl.exe
    • winbnl.exe

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• 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.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. 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.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.