3100  (250-1632)           Computer Viruses            Faxback Doc. # 5512

A computer virus is a program intended to destroy systems by corrupting
data.  Diskettes, networks, and modem transfers can carry viruses.  When
files from an infected computer are used on another system, the virus
spreads.

Problems might occur as soon as the virus invades the system, or the
virus might wait for a preset time before becoming active.

Prevention

Viruses spread through contact with other systems via diskettes, modems,
and networks.  To protect your system:

-Use virus-checking software to scan new diskettes and new files before
 coping or using them.

-Use only write-protected master copies to make backups.  Make copies
 after you start up with a write-protected diskette.  Start up by
 resetting the computer or pressing the power button, not by pressing
 CTRL+ALT+DEL.

-Always keep a write-protected copy of a startup diskette.  If a virus
 infects your hard drive, you still start up with this diskette.

-Keep copies of files on write-protected diskettes.

-Be wary of copied or pirated software.

-Do not assume that legitimate, packaged software is free of viruses.

-Contact your computer dealer or your public library for information
 concerning virus protection.

Diagnosis

Virus symptoms can mimic symptoms of simpler hardware problems, such as
bad cable connections or poor SIMM contacts.  Follow the suggestions in
the earlier troubleshooting suggestions to correct problems.  If you think
your computer has a virus, use current virus-scanning programs that can
recognize recent viruses.

(smc-01/04/94)