The worm that invades computers

''A Novel of Terror in the Computer Age,'' read the card announcing Theodore Roszak's forthcoming book ''Bugs'' (Doubleday & Co.). It envisions an ''infestation of voracious bugs throughout the world's computer systems. Soon modern society, totally dependent on the technology of computers, grinds to a halt. . . .''

This bit of fiction had a disturbing ring of verisimilitude.

Computers now are essential for defense, finance, much manufacturing, and delivery of a variety of services including production of this newspaper. Computer bugs - electronic, not biological - are an all-too-frequent menace that can paralyze whole systems.

And to show that reality anticipates science fiction, Jon Hupp and John Shoch at the Xerox Research Center in Palo Alto, Calif., have developed an an aggressively invasive computer program that does essentially what Roszak has in mind. They call it ''WORM.'' It worms its way into other computers interlinked on a network, replicates itself, and destroys any programs they were running.

At the laboratory, the two computer scientists had access to a network of 100 small computers linked by a system called Ethernet, which Digital Equipment, Intel, and Xerox Corporations have fostered. Hupp and Shoch explained last winter that they left their WORM program running on a few of these computers overnight. By morning, it had invaded dozens of other machines, putting them out of action.

If one of these machines were restarted, it would soon be invaded by WORM again. Every invaded computer on a network must be cleared and reprogrammed to get rid of the menace.

Hupp and Shoch do have other programs to control their wily WORM. One of these, called WORM-Watcher, can monitor WORM's progress as well as restrict its action or purge it from the network. Also, WORM will work only with Ethernet and the particular kind of computers the researchers were using. There is little danger of this WORM somehow escaping and bringing Roszak's novel to life.

Nevertheless, it does have ominous overtones. Much of the work done on computers is actually performed with machines that are parts of networks - airline ticketing, for example, banking, or even the dispatch of this column from the computer on which it is written to the computer complex where it is edited and set in type. Programs such as WORM that can wander through these networks may find wide application for good or evil.

Hupp and Shoch foresee such useful tasks as searching out information lost in a complex computer network and returning it to the inquirer. Or the peripatetic program might seek out unsuspected faults in a network. But it also could be used for spying and other mischief.

One wonders if Roszak realizes how perspicacious his ''Novel of Terror'' may actually be.