For more information on Word macro viruses, see the description of Concept.
WordMacro/Friday consists of several macros, all of which start with the text 'NOP'. However, the virus is not related to the WordMacro/NOP virus.
On every Friday the 13th the virus renames IO.SYS to I_O.SYS, making the machine unbootable if the operating system is Windows 3.x or Windows 95. On Friday the 13th the virus also encrypts all saved files with the password "Friday13".
In addition, the virus exits Windows between 11:00 and 11:59 on Saturdays, encrypts documents with a password equal to the last three letters of the document name on Saturdays, protect the document with a password equal to the first 4 characters of the document name on Thursdays before 11 or on Wednesdays, exits Windows on Wednesdays after 23:00, etc.
WordMacro/Friday was reported to be in the wild in Germany in January 1997.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Technical Details: Vesselin Bontchev, Frisk Software International