W32.Gaobot.EUX

1. Checks for the presence of a debugger and terminates itself if one is found. The worm will also terminate itself if it detects that it is running on a VMware virtual machine.
   
   
2. Copies itself as the following file:
   %System%\netbtd.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. Registers itself as the following service:
   
   Service name: NetBTD
   Display name: NetBTD(ntbtd)
   Image path: %System%\netbtd.exe
   Description: Net bios background information transfer service.
   
   so that it is executed every time Windows starts:
   
   
4. Creates the following registry subkey to create the above service:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBTD
   
   
5. Adds the following registry entries:
   
   "ImagePath" = "%Windir%\netbtd.exe"
   "DisplayName" = "NetBTD(ntbtd)"
   "Description" = "Net bios background information transfer service."
   
   to the following subkey:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBTD
   
   
6. Creates the following registry subkey:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\ENUM\ROOT\LEGACY_NETBTD
   
   
7. Modifies the following registry values:
   
   "UpdatesDisableNotify" = "1"
   "AntiVirusDisableNotify" = "1"
   "FirewallDisableNotify" = "1"
   "AntiVirusOverride" = "1"
   "FirewallOverride" = "1"
   
   in the following registry subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
   
   to lower security settings.
   
   
8. Modifes the following registry value:
   
   "EnableFirewall" = "0"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\DomainProfile
   
   to lower security settings.
   
   
9. Modifes the following registry value:
   
   "EnableFirewall" = "0"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\StandardProfile
   
   to lower security settings.
   
   
10. Modifes the following registry value:
    
    "AUOptions" = "1"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update
    
    to lower security settings.
    
    
11. Modifes the following registry value:
    
    "Start" = "4"
    
    in the registry subkeys:
    
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TlntSvr
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RemoteRegistry
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Messenger
    
    to lower security settings.
    
    
12. Modifes the following registry value:
    
    "restrictanonymous" = "1"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    
    to lower security settings.
    
    
13. Modifes the following registry values:
    
    "AutoShareWks" = "0"
    "AutoShareServer" = "0"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
    
    to lower security settings.
    
    
14. Modifes the following registry values:
    
    "AutoShareWks" = "0"
    "AutoShareServer" = "0"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation\parameters
    
    to lower security settings.
    
    
15. Modifes the following registry value:
    
    "DoNotAllowXPSP2" = "1"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
    
    to lower security settings.
    
    
16. Modifes the following registry value:
    
    "EnableDCOM" = "N"
    
    in the registry subkey:
    
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE
    
    to lower security settings.
    
    
17. May also attempt to delete network shares.
    
    
18. Stops the following services:
    
    
    • Tlntsvr
    • RemoteRegistry
    • Messenger
    • SharedAccess
    • wscsvc
      
      
19. Opens a back door by connecting to the following IRC server:
    
    frayedendsofsanity.be
    
    on the following TCP port:
    
    5599
    
    which allows the remote attacker to perform the following actions on the compromised computer:
    
    
    • Download files
    • Update itself
    • Scan open ports
    • List and terminate processes
    • Get information relating to the Internet Explorer start page
    • Gather system information such as CPU, memory, etc
    • Read, write, and delete registry values
    • Perform denial of service attacks
    • Flush the DNS and ARP caches
      
      
20. Attempts to copy itself to remote machines based on a list of randomly generated IP addresses.
    The worm uses a hardcoded list of passwords against the list of users obtained from the remote machines.
    It will copy itself to one of the following:
    
    
    • IPC$
    • Admin$
    • Admin#\system32
    • c$\winnt\system32
    • c$\windows\system32
    • d$\winnt\system32
    • d$\windows\system32
      
      
      and the passwords used are:
      
      
    • administrator
    • admin
    • root
    • 1111
    • 12
    • 123
    • 1234
    • 12345
    • 123456
    • 654321
    • !@#$
    • !@#$%
    • !@#$%^
    • !@#$%^&
    • asdf
    • asdfgh
    • server
      
      
21. May spread through AOL Instant Messenger by modifying info.backup and info.htm in the AIM directory.
    
    
22. Spreads to computers by exploiting the following vulnerabilities:
    The Microsoft Windows Local Security Authority Service Remote Buffer Overflow (as described in Microsoft Security Bulletin MS04-011) using TCP port 445
    The Microsoft Windows DCOM RPC Interface Buffer Overrun Vulnerability (described in Microsoft Security Bulletin MS03-026) using TCP ports 135 and 445
    The Workstation Service Buffer Overrun vulnerability (as described in Microsoft Security Bulletin MS03-049 using TCP ports 135 and 445
    The Microsoft Windows Plug and Play Buffer Overflow Vulnerability (described in Microsoft Security Bulletin MS05-039) using TCP ports 135 and 445
    The Microsoft Windows ASN.1 Library Bit String Processing Variant Heap Corruption Vulnerability (described in Microsoft Security Bulletin MS04-007) using TCP ports 135 and 445

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.