W97M/Gullible is a Word 97 macro virus that replicates when an infected document is opened. It infects the global template and all documents that are currently open. After the global template is infected it also infects all documents created, opened or closed after that.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
If the name of the registered user is "S. Bach", and an infected document is opened the virus displays a message in German:
Ich bin wieder hier!
which means "I'm here again!" in English.
At March 19th the virus activates its payload when an document is closed. At this time the virus will change the shape of Word window to a circle.
Then it uses Office Assistant to show two messages. The first message is:
(DocumentName) was infected by MFV (My First Virus)
where "(DocumentName)" is replaced with either the document name or the name of the global template, "Normal.dot".
The second message is:
This virus is not harmful. Belive me! Your window was only deformed, not more! This virus is freeware. You may give it to anyone!
After the virus has modified the appearance of the Word window, it has to be closed from task bar or using a hot key (Alt+F4) since the menu bar is partially invisible.
Technical Details: Katrin Tocheva and Sami Rautiainen, F-Secure