W32.HLLW.Antinny.G

W32.HLLW.Antinny.G is a variant of W32.HLLW.Antinny, a worm that propagates through the Winny peer-to-peer file-sharing network. When the worm is executed, it displays a fake error message and creates the following copy of itself in a randomly chosen folder with one of the following filenames:

Svchost.exe
Spoolsv.exe
Explorer.exe
Winlogon.exe
Explorer.exe

It then creates a randomly named copy of itself using the name of a file on the system (chosen randomly) and adding random characters to it. This file will be created in the same directory as the original file.

It then creates the following registry entry to launch this randomly named file every time Windows starts:

"[randomly chosen program name]"="[path to worm]" [/logon, /start, /autorun or /startup]

To registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

The worm then attempts to delete files on the C drive. Following that, it overwrites %Windir%\Regedit.exe and %System%\Regedt32.exe with Notepad.exe. It then attempts to collect personal information by reading name, organization and e-mail address values from the registry. This information is stored in a text file.

The worm then creates a copy of itself in the Winny upload or download directory, selecting one of several hardcoded Japanese strings as its filename. It then creates a HTML file that will execute the worm if clicked. The HTML file will have a .htm or .folder extension and a standard Windows icon. The worm then stores screen captures in the Winny upload or download directory.

Finally, the worm will create a .zip or .lzh archive containing the personal information and, possibly, a copy of itself and the HTML file and screen capture image files. The archive will be stored in the Winny upload or download directory.

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