Virus Profile: W97M/Chack.BZ

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Virus Profile information details
Risk Assessment: Home Low | Corporate Low
Date Discovered: 8/1/2000
Date Added: 9/13/2000
Origin: Unknown
Length: N/A
Type: Virus
Subtype: Macro
DAT Required: 4090
Removal Instructions


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

Macro warning when opening infected documents on non-infected systems and the macro warning option is enabled before hand.

This virus contains a date activated payload to show the user form graphic; the graphic is displayed when an infected document is closed, if the current date is August 1st.

Methods of Infection

This virus hooks several Word event handlers in order to run its code:
Opening/closing/saving documents

The following menu options are intercepted in order to run its code:


Virus Characteristics

This is a macro virus for Word97/2000 documents and templates. This virus does not have a destructive payload. This virus will lower macro warning settings and remove some menu options such as "Tools|Macro". This virus will also attempt to disable the hotkeys for starting the Visual Basic Editor "ALT-F11".

This virus contains one macro module named "Km" and one user form module named "Km". The user form contains a graphic image which is displayed on August 1st.

All Users :
Script,Batch,Macro and non memory-resident:
Use current engine and DAT files for detection and removal.

PE,Trojan,Internet Worm and memory resident :
Use specified engine and DAT files for detection. To remove, boot to MS-DOS mode or use a boot diskette and use the command line scanner:


Additional Windows ME/XP removal considerations

Users should not trust file icons, particularly when receiving files from others via P2P clients, IRC, email or other mediums where users can share files.

AVERT Recommended Updates :

* Office2000 Updates

* Malformed Word Document Could Enable Macro to Run Automatically (Information/Patch )

* scriptlet.typelib/Eyedog vulnerability patch

* Outlook as an email attachment security update

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

For a list of attachments blocked by the Outlook patch and a general FAQ, visit this link .
Additionally, Network Administrators can configure this update using an available tool - visit this link for more information .

It is very common for macro viruses to disable options within Office applications for example in Word, the macro protection warning commonly is disabled. After cleaning macro viruses, ensure that your previously set options are again enabled.


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