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Virus Profile: VBS/Tam@M

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Virus Profile information details
Risk Assessment: Home Low | Corporate Low
Date Discovered: 10/12/2000
Date Added: 10/13/2000
Origin: France
Length: N/A
Type: Virus
Subtype: Internet Worm
DAT Required: 4100
Removal Instructions
   
 
 
   

Description

This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.

Indication of Infection

Recipients of messages which contain VBS/Out@M may receive warning messages such as:

"Do you want to allow software such as ActiveX controls and plug-ins to run?"

Users should select "NO" to this question. Also another warning dialogue box could be displayed:

"Scripts are usually safe. Do you want to allow scripts to run?"

Users should select "NO" also to this question. Further indications of infection are the existence of files OUT.HTA, OUT.HTML and TAM.HTA as previously mentioned, and added or modified default signature.


Note - "C:\WINDOWS\OUT.HTA" is only created on the French version of Windows9x

For the French versions of Windows 9x:
- Existance of "c:\windows\menu démarrer\programmes\démarrage\tam.hta"
- On August 30, a message is displayed:


Bon Anniversaire Lac !!!
      Un ami...

This box will reappear after "OK" is clicked. On the 5th click, this message appears:
KOI??? Ca t'interresse pas? 
Tu n'es pas digne du monde informatique.
BYE-BYE
Clicking OK to this message results in your computer shutting down.

Methods of Infection

Opening email messages which are composed in HTML format and which contain the script will install the Internet worm on supported systems as previously describede. The HTA file is written to the local machine as is the HTML.

Aliases

Kak.D, out.hta, tam.hta, VBS/Kakworm-D, VBS/Out.A@m
   

Virus Characteristics

This worm functions much the same way that JS/Kak.worm does. AVERT recommends installing the security patch from Microsoft mentioned below.

Like JS/Kak.worm, a dangerous aspect of this Internet worm is its ability to continuously re-infect yourself if the preview pane is enabled and you browse between folders specifically the "sent" folder which happens to contain the Internet worm within a message. This is another strong reason to update to the security patch.

This worm uses VBScript and an ActiveX component, called "Scriptlet Typelib", to propagate itself through email using MS Outlook Express.

When an e-mail or newsgroup message infected by this worm is opened by a reader which supports VBScript in HTML, the writes the Update.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

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, then this file is written to the local machine:

"C:\WINDOWS\OUT.HTML"

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\OUT.HTML" and is set as the default signature such that the worm is spread on all outgoing email if the signature is included.

A value is added to the registry: "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\
Run\OnGoingCtrl=c:\windows\out.hta"
Note - The "C:\WINDOWS\OUT.HTA" file is only created on the French version of Windows 9x.

For the French versions of Windows 9x:
- Writes a copy of itself to "c:\windows\menu démarrer\programmes\démarrage\tam.hta"
- When "TAM.HTA" is ran at startup, "C:\OUT.HTA" is created.
- On August 30, a message is displayed:


Bon Anniversaire Lac !!!
      Un ami...

This box will reappear after "OK" is clicked. On the 5th click, this message appears:
KOI??? Ca t'interresse pas? 
Tu n'es pas digne du monde informatique.
BYE-BYE
Clicking OK to this message results in your computer shutting down.
   
Use specified engine and DAT files for detection and removal.

Removal of this Internet worm consists of several steps:

* close email client(s)
* install the MS patch mentioned above
* remove the .HTA and/or .HTML files associated with this threat
* turn off 'preview pane' (optional)
* delete the default email signature setting (Tools/Options/Signature)
* delete messages which are not needed which may contain the embedded script

Users may also benefit by removing Windows Scripting Host from their Windows environment. To do this in Windows 9x, go to 'Control Panel' and choose 'Add/Remove Programs'. Click on the 'Windows Setup' tab and double click on 'Accessories'. Scroll down to 'Windows Script Host' and uncheck it and choose 'OK'. It may be necessary to reboot the system. For additional help or support, visit Microsoft's Support Site .

Users may also want to disable 'Active Scripting' in the 'Restricted Sites' zone and set E-Mail to run in the 'Restricted Sites' zone. To do this:

-open Internet Explorer
-choose the Tools menu
-choose Internet Options
-click the Security tab
-click the Restricted Sites icon
-click 'Custom Level'
-scroll down to 'Active Scripting' and set it to Disable or Prompt
-Click OK
-open Outlook
-choose the Tools menu
-choose Options
-click the Security Tab
-In the 'Security Zones' section, choose the 'Restricted Sites' zone

AVERT Recommended Updates :

* scriptlet.typelib/Eyedog vulnerability patch

* Malformed E-mail MIME Header vulnerability patch

* Exchange 5.5 post SP3 Information Store Patch 5.5.2652.42 - this patch corrects detection issues with GroupShield

Additionally, Network Administrators can configure this update using an available tool - visit this link for more information .