The bombers are among us and we'll never know their names

Brainy, barmy outsiders want to wreak revenge on society. And now, says David Aaronovitch, they have the anonymous cyber-help to do it

IT'S BAD enough when the harassed supermarket check-out girl hurls your yoghurts on top of your eggs while you scramble shoulder-deep in plastic bags, trying desperately to pack your shopping, before the mineral water obliterates both your comestibles. But now you can't even go to Sainsbury's without some lunatic trying to blow you up.

On Wednesday another explosive device went off close to a branch of the store in the London suburb of Forest Hill. The police said that it "bore all the hallmarks" of the Mardi Gra bomber (is there - in the East End perhaps - some little unshaven underworld explosives expert, who spends his life chiselling initials or symbols on the sides of bombs attesting to their quality?).

We will return to this scourge of suburban shoppers later, for, by interesting coincidence, also on Wednesday two other ominous things happened; one in the English Home Counties, and the other - as reported in this newspaper - in the United States. In Bexleyheath, Kent, two 16-year-old boys were questioned about three blasts in just over a fortnight, caused by home- made pipe-bombs. A search turned up some chemicals and three more unexploded bombs. At a guess these probably bore all the hallmarks of naughty schoolboys.

And over the water the Americans were experiencing "cyberterror", a rather overblown phrase for the temporary freezing of a few terminals.

Nevertheless the implication of the attack - that somebody could and would use the Internet to disable vital operating systems from afar - caused unsurprising consternation.

Join the dots together and it's all a bit worrying, isn't it, this pattern of anonymous assaults? Since 1994, when he first wrapped six devices in Christmas paper and delivered them to Barclays bank, Mardi Gra has been credited with 33 attacks. One of his current tricks appears to be leaving a shopping bag with a bomb in it at bus-stops, where old ladies and others pick them up along with their own shopping, and cart them back to Dunroamin for unpacking. Such a strategy does not suggest a kind heart. The explosions are bound to get bigger and louder and better publicised, until some poor innocent sod dies. He reminds one irresistibly of the reclusive maths don Ted Kaczynski - the Unabomber - who killed several people with bombs mailed from his kennel in the mountains of Montana.

Meanwhile the cyberterrorists are on the march. Some of the worries about their activities can sound silly. One site warns that cyberterrorists could do you over when, "all those electronic publications you've subscribed to are mysteriously vaporised, because somebody discovered your passwords and unsubscribed you". Bang goes your passport to an unbiased survey of international news courtesy of The Times. You'll survive. However the potential impact, variously, of viruses, worms, logic bombs, Bots. and SYN attacks, has led the US National Security Agency to employ 1,000 cyberdefenders in "an information warfare department". The worry is that teen hackers could, according to E magazine, "cripple the United States information infrastructure during the height of holiday travel. Onboard computers could redirect planes into conflicting flight paths. Subway systems could be shut down or reprogrammed for collision. And that's just for starters." Philip LaCombe, the director of the President's commission on critical infrastructure protection, is quoted as warning that "the capabilities to launch an attack against the nation's information infrastructures are now quite widespread, and an attack is probably not that far away". All right. There's the threat. But who are these guys? Why are they doing all this? On Thursday the police described the hunt for the Mardi Gra bomber as being like looking for a "small needle in a very large haystack". Not least because there seemed to be no motive for wanting to blow up Sainsbury's shoppers. "We don't know why he's doing it!" one officer said plaintively on television on Thursday.

They'd done their profiling though and come up with "a business man with a grudge". Yessss. It is certainly true that such profiling worked for Kaczynski, but the businessman theory seems far-fetched. What does seem likely is that Mardi Gra is educated, inadequate and - above all, alienated. Contemporary capitalist society with its emphasis on achievement and materialism and its destruction of community has given birth to a whole geological stratum of brainy, barmy, outsider-type guys who want to see how far they can - alone and unassisted - take on and defeat that society. Scary.

Very scary because it's so easy to do. So let me warn you that, should you write me one of those whining, complaining letters that readers sometimes do - pointing out some minor error of fact or interpretation - don't put your address on it. Because I could kill you.

Today, as I sat here at my terminal, I put two words into an Internet Search Engine and discovered how to blow you up. The author of the article in question confided in me how to build a home-made shotgun shell mine, a driveway pipe mine and - best of all - a letter bomb. Using language as accessible as that of a Blue Peter presenter, he told me what to buy, how to put a device together and even how to tailor it to my own specialised needs. Did I want shrapnel, or would I rather do without? Each helpful section began with a general introduction, as in "Letter bombs have the great advantage that you can send them anywhere in the World. I have successfully mailed these throughout North America." Then a practical DIY bit: "To make a letter bomb the way I do ... fold over the open end of the envelope and staple it closed once or twice." And the advice ended in a final encouraging flourish: "Mail it off to your target and when they open it and try to remove the papers ... BOOM!"

If this gives you nightmares then there are ways that you can guard against such unwelcome packages. A Net security site suggests that you watch out for: grease stains, too many stamps (the last thing a bomber wants is for the damn thing to be returned stamped "inadequate postage"), if it is mailed from an "unfamiliar location" - like Bexleyheath for instance - or if there is the odour of almonds.

But what is truly amazing about this Doomsday stuff - given the alienation, the anonymity, the availability of the technology, society's vulnerability and all that - is how remarkably little it happens. Compare the incidence of Mardi Gra explosions, teenage suburban bombers and cyberterrorism with those other activities that tell of male disaffection: lobbing concrete off motorway bridges, stabbing people outside discos, or - most common of all - filling the car with carbon monoxide while still inside it. Whose hallmarks do these sad activities bear?