F-Secure Virus Descriptions : W97M/Walker

NAME:	W97M/Walker
ALIAS:	Walker

VARIANT: Walker.D

ALIAS: SAT, Sattelite

W97M/Sattelite (also known as W97M/SAT) is a Word macro virus with extraordinary functions.

This virus encrypts and decrypts it's own code on-the-fly, making analysis and detection of the virus problematic. The encryption is done with multiple layers of XOR-based substitution.

Sattelite spreads whenever Word documents are opened or closed. It detects that it has already infected a document by searching for this text in the documents macros:

        SATTELITE V1.5

The virus activates by modifying the registry so that the registered owner name of Microsoft Windows will be changed to:

        ThE wEiRd GeNiUs

This will work only under Windows 95 and Windows 98.

Sattelite was widespread in Northern Europe in early 1999.

VARIANT: Walker.E

W97M/Walker.E is a slightly modified variant from W97M/Walker.D. The difference is that this variant uses the following string as a marker:

    SATTELITE V1.0

This variant does not alter the name of the registered owner of Windows.

VARIANT: Walker.L

W97M/Walker.L is an encrypted class infector that infects the global template when an infected document is opened. After the global template has been infected, the virus infects all documents that are opened or closed.

The virus also lowers the security settings of Word 2000, and disables all selections from the "Tools/Macro" menu.

It uses the following string to determine if the document is already infected:

    [Bench]Garbage v2.0

[Analysis: Katrin Tocheva and Sami Rautiainen, F-Secure]