It's an unwise business that powers up its computers without testing them with virus-checking software. When a technician at Nevamar, an industrial laminator in Odenton, Md., turned on a company computer one recent weekend, he was startled by the message "You shouldn't be working on a Sunday. Ha-ha!" The files had been rendered sausage, an apparent casualty of the infamous Sunday Virus.

Unleashed indiscriminately by heinous hackers, viruses are insidiously spread via infected floppy disks, often reducing critical files and backups to gibberish. Many viruses can be cured if they're discovered early. But no sooner is one version of antiviral software made available than vandals devise diabolical ways to confound it. That challenge has been met by Microcom, which releases an updated version of its detection, eradication, and prevention program (for IBM or Macintosh, $99.95; 919-490-1277) as frequently as is necessary, and gives registered users of the IBM version six months' worth free. Even so, safe computing is bound to be more expensive than safe sex: as of the start of 1992, more than 500 viruses had been identified, with new ones cropping up at the rate of 10 a week. -- Robert A. Mamis