Suppose that World War III could be fought without a single shrieking missile or mound of sizzling ash -- that it were waged instead on cool and bloodless plains of silicon and won by software sabotage of the enemy's crucial computer systems.

That is the timely and arresting premise of "Softwar," a French techno-thriller jointly created by a Parisian programmer and a New York writer. A best seller in France last fall, it has just been published here in a briskly readable English translation by Mark Howson.

Brendan Barnes, a young computer-science professor at MIT, is recruited by a clandestine offshoot of the Pentagon for an ultrahush mission: The surreptitious insertion of "software bombs" into the central Soviet computer network.

It's more than plausible. High-powered programs frequently run to lengths that make "Paradise Lost" look like a grocery list; millions of lines amounting to a syntactical haystack in which to hide a needle of code. And what a bang for the buck: Sneak a few killer glitches into the instructions and "any sector of a society can be . . . completely paralyzed," says the U.S. project boss, "simply by a couple of keystrokes on a computer terminal, anywhere in the world. We do definitely see this as the electronic battleground of the future."

Better yet, the Soviet Union is practically wearing a "kick me" sign. As the novel opens, the cybernetically retarded Reds, desperate for western hard- and software, are about to purchase a highly advanced American computer and a huge weather-forecasting program from the French. As expected, intrigues abound.

Little do the French know that the Moscow warlords have Nefarious Other Plans for the big rig. Little do the Russians know that Brendan has diddled the code with a hidden "bug" designed to crash the system on remote command. (Just a test: If that legerdemainframe works, he'll write a humdinger that'll wipe out everything but the graffiti in the Kremlin's men's room.)

But little does Brendan know that the top tomato of the Soviet Union's computerati is none other than his former graduate-exchange student and lover, the succulent Yulya Voronkov, now married to an upwardly mobile KGB type named Sergei. Little does Sergei know that their daughter, the precocious, sloe-eyed Svetlana, is in fact Brendan's child from the Cambridge tryst, or that Yulya's researches have turned up a fiendish perfidy at the heart of her government. And more, alors!

So far, so good. The authors are unstintingly inventive, devising several dozen characters in numerous international settings. They wring every exploitable wrinkle out of the plot, assiduously explore its political ramifications and provide ample historical background. The result verges on the novel of ideas, with all its gabby propensities. Each new development gets a thorough palaver by the principals, then is mulled by the Pentagon boys, then chewed over in Moscow, frequently with infuriating redundancy. Unhappily, such action as there is (chiefly bug planting, bug detonating and bug hunting) tends to be too cerebral to offset the incessant yacking, and windburn is a constant threat.

Consequently, readers anticipating the familar frissons of the thriller genre may be disappointed. Too often even the most potentially exciting junctures sag to anticlimax, since life, limb and world peace are never seriously in jeopardy. Sure, there's a perfunctory attempt on Brendan's life and Yulya endures a grilling, but neither ever seems or feels in real danger; indeed, the chief terror in the book is that the Russians, having uncovered Brendan's meddling, will announce it at a computer convention in Geneva, thus scoring a propaganda coup, threatening the embargo on high-tech sales to the Soviet Union and diminishing U.S. computer exports. Dreadful, certainly, but not likely to make you lurch for the heart pills. Even the softbombs prove duddish. Yulya's aide Kutuzov exclaims of Brendan's first bug, "Whoever thought this up is a genius pure and simple." Yet Kutuzov, a notorious sot who repairs to the computer center after a guzzling spree at a bordello, detects it in only a few hours. Ditto for another, more sinister contrivance, which Yulya conveniently finds by accident.

Still, readers who have watched the automated teller gizmo eat their bank cards, lost their tax refunds to "computer error" or received a six-digit credit-card bill for charges they never made will realize how profound is the computer's hold on our lives. That's the context in which "Softwar" is chillingly apt. And if not fully satisfying as a novel, it's terrific as vicarious revenge.