Virus Profile: W97M/Class.ed

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Virus Profile information details
Risk Assessment: Home Low | Corporate Low
Date Discovered: 10/29/1999
Date Added: 11/15/1999
Origin: N/A
Length: N/A
Type: Virus
Subtype: Macro
DAT Required: 4051
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 if opening infected document, increase in size to global template. File SYSTEM.SYS created in root of C:, menu items removed from Word97 on the 15th as mentioned above.

Methods of Infection

Opening infected documents will infect global template


W97M/, W97M/Class.ed, WM97/Class-ED

Virus Characteristics

This is a virus for Word 97 documents. It is able to replicate under the SR-1 release of Word 97. It will turn off the macro warning feature of Word 97. This virus uses the "ThisDocument" stream when infecting documents and templates. It is based on the original W97M/Class family by the use of inserted comment lines between each line of code to cause variable polymorphism. A temp file is created in the root of c: drive named "SYSTEM.SYS" to use as an import and export for the virus infection routine. This file contains the source code of the virus.

This virus hooks the system event of opening Word97 by the subroutine "autoopen" thereby running its code. Other system events hooked are "toolsmacro" and "viewvbcode". Attempts to use menu items of the same name within Word97 will run the macro code routine.

This virus does not modify the registry as with other W97M/Class variants.

On the 15th of any month, the following menu choices are deleted from the Word97 environment:
"File | Page Setup..."
"File | Print Preview"
"File | Print..."
"File | Exit"
"File | New..."
"File | Open..."
"File | Close"

If selecting "Tools|Macro|Macros" or "Tools|Macro|Visual Basic Editor" menu options, the following message is displayed: "This program has performed an illegal operation and will shut down."

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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