W32.Gubed.int

When W32.Gubed.int runs, it does the following:

It searches the following files for email addresses:

• Index.htm
• Index.html
• Index.asp
• Default.htm
• Default.html
• Default.asp
• Main.htm
• Main.html
• Main.asp

It then attempts to send the following email message to all addresses that it finds:

Subject: Congratulations for your site

Message:
Congratulations for your site
This is a good tool to improve it.
Best Regards.

Attachment: WebMakeFullInstall.exe

The worm also drops a script that is a second, intended mass-mailing worm. It attempts to send itself to all email addresses that are in the Microsoft Outlook Address Book, but due to bugs in the code, the worm does not perform the mass-mailing function. If it were successful, the email message would have the following characteristics:

Subject: Important EMail for [recipient's name]
Message: Look at this attached file, it may be important.
Attachment: Start.vbs

W32.Gubed.int then copies itself to \%System%\DebugW32.exe. It then adds the value

Debug     %System%\DebugW32.exe

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

so that the file runs when you restart Windows.

The worm also creates \%Windows%\Start Menu\Programs\StartUp\Start.vbs. This VBScript attempts to search the My Documents folder and its subfolders for files that have the .vbs extension. The worm attempts to overwrite each file with Start.vbs, but due to bugs in the code, the script does not perform this action.

Finally, the worm copies itself five times to both the \Windows and the \Windows\System folders. To do this, the worm searches for an .exe file, copies the file name, and appends "_vbpe.exe" to it. For example, if it finds Actmovie.exe, it copies itself to Actmovie.exe_vbpe.exe. It does this for five files in both folders.

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.

Summary