Wscript.KakWorm

Wscript.KakWorm is a worm. It spreads using Microsoft Outlook Express. The worm attaches itself to all outgoing messages using the Signature feature of Outlook Express. Signatures enable you to automatically append information at the end of all outgoing messages.

This worm uses three files to deliver its payload. The file extensions are:

• .hta
• .reg
• .bat

The message that contains this worm is written in an HTML format that supports scripting. It uses a security hole in Microsoft Outlook/Outlook Express that is known as "Scriptlet TypeLib," and it places a shortcut to an .hta file in the StartUp folder. The next time the computer is restarted, the .hta file is run.

NOTE: While computers running either unpatched Microsoft Outlook or Outlook Express can be infected, only Outlook Express can automatically spread the infection.

This worm can reinfect your computer if it is displayed in the preview pane of Outlook Express. This can happen when switching between folders. (This means that a viral file can be created on the system without having to open an attachment.) This can be prevented by applying Microsoft's security update patch. With this update, you are asked whether you want to run the ActiveX control which is marked "safe for scripting."

If you have a patched version of Outlook Express, then this worm will not affect you. To obtain the Microsoft patch, go to http://www.microsoft.com/TechNet/IE/tools/scrpteye.asp. Additional information is available at this location. Most users will want to download the Intel version.

If a system is infected, then there will be no real indication of this until the first day of any given month. On the first of the month you will see the following message:

"Kagou-Anti-Kro$oft says not today!"

If you click OK, the computer shuts down. This window returns each time you start Windows.

NOTE: As noted previously, Wscript.KakWorm is spread as part of an email message--not an attachment. If, however, your email program or the email server that handles the message is not set up for or capable of handling HTML encoded messages, the program or server will convert the encoded message to an attachment. This attachment usually has a name such as Att1.htm. If you open the attachment, it can have the same effect as if you received the email message with the worm embedded.

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