BOOK REVIEW / Dumpster diving with Captain Zap and Fry Guy : Scott Bradfield on the lonely world of hackers: 'Approaching Zero' - Bryan Clough & Paul Mungo' - Faber, 14.99 pounds

TODAY'S gangsters tend to look a lot like yesterday's geeks - late-blooming male adolescents without girlfriends who attend science fiction conventions, read too many comic books (oops, make that graphic novels), live with their parents and spend too much time alone in their rooms. Hopped-up on everything from benzedrine to Diet Coke, they are the western world's new kingpins of crime, hacking their way into top secret information systems at the Pentagon, war dialling into consumer credit services, unleashing deadly viruses and data-detonators.

According to Bryan Clough and Paul Mungo's fascinating new book, Approaching Zero, almost every major computer system in the world has been hacked, from Nato to Nasa, and the cost to US and UK citizens alone has been estimated at pounds 2bn per year. But the emphasis here is on 'estimate.' As much as 85 per cent of computer crime may go unreported or undetected. According to Clough and Munro, contemporary 'hacking' originated as a form of telephone fraud in the mid-1960s called 'phreaking'.

Among America's notable early phreakers were Steve Jobs and Steve Wozniak, manufacturers of the infamous Blue Box (an electronic gizmo used to access long-distance telephone lines); known as 'the two Steves', they went on to found Apple Computers, the world's first major producer of low-cost PCs. Then there was Captain Crunch (aka John Draper), who tapped into Bell service lines using nothing more sophisticated than a plastic whistle that was being distributed in Captain Crunch Cereal; he was later enlisted by Abbie Hoffman and the Yippies, served time in jail (where he swapped the secrets of his trade with drug pedlars in exchange for personal protection), and eventually went to England to help train the first generation of British hackers.

Hacking is the art of the lonely and the vain, young obsessive men with hyperactive imaginations who are brave enough to journey into the theoretical spaces of their computer screens and come back with other people's money. It's a profession as abstract and anti-social as dealing junk-bonds or corporate raiding, and just as profitable. Top- notch hackers have committed extortion, fraud, gang warfare, international terrorism, espionage - and usually without leaving the privacy of their bedrooms. Many of their weapons originated as birthday and Christmas toys from their parents.

Some hackers are politically motivated, like the Galactic Hackers Party, who declared in the late 1980s: 'The free and unfettered flow of information is an essential part of our fundamental liberties.' If the information doesn't freely flow, these New Age Robin Hoods believe it should be forcefully redistributed, like cash or vegetables. On the other hand, some hackers want to make a few (or even a few million) quick bucks. Still others want nothing more than to vandalise and break things, tracking their muddy boots through high-security information networks and scrawling their names on the walls.

As the Mad Hacker, Nick Whitely, once confessed, the excitement of hacking 'comes from knowing that a computer in the bedroom at home can be used to get into multi-million pound installations. There's a sense of exploration, of going around the world electronically. The objective is to try to get the highest status within the system, that of system manager. Once there, you start making the rules instead of following them'. Some hackers are motivated by the love of knowledge; others by the love of destroying it.

High-profile hackers assume nicknames such as Fry Guy (lifted from the old MacDonald's jingle, 'We are the fry guys'), Phiber Optik, Captain Zap, Doctor Diode and Triludan the Warrior. Sometimes they run in hi-tech 'street gangs' with names like Masters of Destruction, Chaos or The Legion of Doom. They are a weird race of lone wolves who rarely meet each other face to face. Instead, they build their reputations through self-congratulatory memos left on electronic 'billboards'. They don't act in the world so much as assert their fantasies of themselves across the humming Worldnet. For this reason, when the authorities intercept anonymous criminal boasts about thefts and acts of sabotage, it's often impossible to tell which crimes really happened, and which were merely imagined.

Clough and Mungo describe what a weird world is occurring all around us, even when we're not looking (or better yet, even when we don't know what we're looking for). But the chief pleasure of this book is its well-annotated glimpse into hacking's glossy lingo, where the meanings of words seem to be proliferating as madly as the information systems themselves. First there are the 'viruses', self-replicating mutable programmes designed to infect computers.

They can be effectively harmless - beeping out a mechanical version of Yankee Doodle, say, or wishing everyone Merry Christmas. They can also be maliciously destructive, indiscriminately destroying hard discs and hard drives, whether they belong to large multinationals or to small PC users like you and me. 'Trojans' (named after the Greek horse, not the American condom) infect systems by teasing the computer operator into letting them in. Then there's 'dumpster diving', the rummaging of garbage cans outside telephone and credit companies to dredge up discarded manuals and instruction booklets; or 'social engineering', which simply means you call up a company pretending to be somebody important, and convince them to tell you secret codes they're not supposed to.

It's a con-game without faces or bodies, just figures on screens, voices on phones, theoretical dimensions on tap, abstract spaces on the brain. It's a world in which criminals make themselves real by falling out of material existence altogether. And it's an invisible world we may all disappear into eventually.

There's no way of knowing how many viruses are out there, or when they're set to go off. The zero hour - that moment when every last bit of information has been eliminated from a system - could very well be approaching now. Clough and Munro contend that when the big data 'bomb' eventually goes off, it could instantly destroy the world's emergency communications networks and information storage systems. It's an end that won't come with a bang, but with a beep.