Virus Profile: JS/Kak@M

Virus Characteristics

Another dangerous aspect of this Internet worm is the ability to continuously re-infect unpatched systems if the preview pane is enabled and you browse messages, including ones in your own "Sent Items" folder, which contain this Internet worm. This is another strong reason to update to the security patch, if not already.*

This is an Internet worm which uses JavaScript and an ActiveX control, called "Scriptlet Typelib", to propagate itself through email using MS Outlook Express. This worm consists of 3 components, an HTA file (HTML Application), a REG file (Registration Entries Update) and a BAT file (MS-DOS Batch).

When an e-mail or newsgroup message infected by this worm is opened by a reader which supports Javascript in HTML, the script checks to see if MS Internet Explorer 5 or higher is installed. If it is, using an ActiveX exploit known as "Scriptlet TypeLib", the script writes the KAK.HTA file to the Startup folder of the local machine. This will launch the code embedded in the HTA file at the next Windows startup. Microsoft has published a security update which addresses this ActiveX exploit and users are encouraged to update their systems with this component. With this update installed, users are questioned if they wish to run the ActiveX control which "might be unsafe".

For more details on this vulnerability and to obtain a patch from Microsoft, see this link:
Microsoft Security Bulletin

To obtain a patch from Microsoft, see this link:
http://www.microsoft.com/msdownload/iebuild/scriptlet/en/scriptlet.htm

For current security bulletins from Microsoft, see this link:
Current Bulletins.

Email messages written in HTML format will be coded with the Internet worm on infected systems due to the default signature modification on infected systems. The email application Outlook is a target of this Internet worm for propagation due to its support for HTML format messages. If an email message is coded with the worm code and it is allowed to run, files are written to the local machine in different locations-

c:\windows\kak.htm
c:\windows\system\(name).hta

kak.hta is written to either folder:
French Windows
C:\WINDOWS\Menu Démarrer\Programmes\Démarrage\kak.hta

English Windows
c:\windows\Start Menu\Programs\StartUp\

In the above list, "(name)" is a seemingly random 8 character name (e.g. 98278AE0.HTA) however it is related directly to a registry entry.

This worm first copies the original AUTOEXEC.BAT file to AE.KAK. Then the AUTOEXEC.BAT file is modified to overwrite the file KAK.HTA and then delete it from the StartUp folder. The system registry is also modified when the script executes a shell registry update using regedit and the REG file written to the local system. The registry modification is this-

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
cAg0u = "C:\WINDOWS\SYSTEM\(name).hta"

The entry "(name)" is an 8 character name (e.g. 98278AE0.HTA).

The email spreading method is possible by a registry modification which adds a signature to MS Outlook. The signature is set to include the file "C:\WINDOWS\kak.htm" and is set as the default signature such that the worm is spread on all outgoing email if the signature is included.

Finally this worm also has a payload which is date activated.

On the 1st of the month, and beginning from 6PM local time, a message is displayed:

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