W97M/Stun.a

This page shows details and results of our analysis on the malware W97M/Stun.a

Download Current DAT: 6712

Threat Detail

Malware Type: Virus

Malware Sub-type: Macro

Discovery Date: 2000-01-20

Next Steps:

Overview
Characteristics
Symptoms
Method of Infection
Removal

Overview

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.

Minimum DAT

4064 (2000-02-09)

Updated DAT

4064 (2000-02-09)

Minimum Engine

5.1.00

File Length

Description Added

2000-01-28

Description Modified

2000-01-28

Malware Proliferation

Characteristics

This is a macro virus which infects Word 97 documents and templates. This virus can infect Word 97 environments which have been updated to SR-1 or higher. This virus writes its code to a temporary file on the local system as "c:\ffastun.drv" in order to transfer to host documents and templates. The use of this name is possibly in order to conceal its identity by using similar names of indexing files created by Microsoft FindFast utility. These files are also stored in the root directory but are not associated with the virus - the files have the same prefix of "ffastun". This virus consists of a single code module named "ffastun". Three system events are hooked by the use of subroutines by the same event name- Autoexec, Autoopen and FileSaveAs.

When opening infected documents, and the date is February 22, a fake error message is displayed of the following, after which an attempt is made to shutdown Windows:

"Illegal function in modul 0xCB15C001"

When printing infected documents, and the date is July 22, the document is printed with a modified footer however this modification is not saved into the document:

"Microsuck Windows - How Do You Want To Crash Today?"
" -= Don't Get Mad With Me, Get UNIX =- "

The following toolbars of both Spanish and English versions of Word97 are removed:

Spanish Word97
Tools | Plantillas y complementos
Tools | Macro
Format | Estilo

English Word97
Tools | Templates and Add-Ins
Tools | Macro
Format | Style

Symptoms

Existence of the file c:\ffastun.drv, message box as mentioned above, macro warning when opening infected documents on non-infected system, toolbars removed as mentioned above.

Method of Infection

Opening infected documents will directly infect the local Word environment and any document used thereafter.

Removal

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:

SCANPM /ADL /CLEAN /ALL

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.