WScript.KakWorm.B

The worm appends itself as a signature to the end of legitimate outgoing messages . When receiving the message, the worm will automatically insert a copy of itself into the appropriate StartUp folder for both English and French language versions.The copy is named Day.hta.

The worm uses a known Microsoft Outlook Express security hole, Scriptlet.Typelib, so that a viral file is created on the system without having to run any attachment. Simply reading the email message will cause the virus to be placed on the system.

Microsoft has patched this security hole. The patch is available from the Microsoft Web site at:

http://www.microsoft.com/technet/security/bulletin/ms99-032.mspx

If you have a patched version of Outlook Express, this worm will not work automatically.

.hta files are executed by current versions of Microsoft Internet Explorer and Netscape Navigator. The computer must be restarted for this file to be executed. Once executed, the worm modifies the registry key

HKEY_CURRENT_USER/Identities//Software/Microsoft/Outlook/Express/5.0/signatures

to add its own signature file, which is the infected Day.hta file. This causes all outgoing mail to be infected by the worm. In addition, the registry key

HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Run/cDays

is added, which causes the worm to be executed each time that the computer is restarted.

Finally, if it is the first of the month and the hour is 17 (5:00 P.M.), the following message is displayed:

Days It was a day to be a days!

and Windows is shut down.

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