On the internet, identity is an unsolved problem. The web's many blogs, forums and chatrooms are populated by users who may not be being candid about who they really are. Many use pseudonyms to shade themselves from the glare of the internet's Panopticon, aware that it might not be appropriate for your boss to find your hen-night snaps via Google. Some conceal their identities to prevent the murky details of their offline past from ruining their credibility as, say, a political blogger. But others have darker reasons for pretending to be someone they are not.

This leads us to the recent furore surrounding the online social networking site MySpace. Now more popular than Yahoo! or Google, MySpace is reported to attract 250,000 new users each day, who sign up to exchange messages, photos and sometimes intimate personal details, with existing "offline" friends and with new pals made online. The problem is that MySpace mixes adults and children in the same social space.

Prompted by a half-dozen legal cases in which children have been preyed upon by adults using false teen profiles, a US House of Representatives subcommittee discussed MySpace this month. "Don't tell me it can't be done. If we can put a man on the moon, we can verify age," the Connecticut attorney general, Richard Blumenthal, said during testimony.

The problem is that, although gambling and pornography sites can verify a user's adult status by demanding credit-card details, most teenagers are not yet on any official databases, and have few means of identifying themselves as legitimately under-age. So would-be Humbert Humberts are free to reinvent themselves in teen profiles designed to lure unsuspecting Lolitas. Having said that, a mere six court cases from a pool of 60 million users is a record that the Catholic Church could only dream of.

Various methods of verifying age have been trialled in the past. The text-based adventure game Leisure Suit Larry in the Land of the Lounge Lizards used a multiple-choice test to confirm that players were adults, with questions ranging from the factual ("Do girls really have cooties?") to the philosophical ("All politicians are: a) hard-working, b) honest, or c) on the public payroll" - the answer to which is c). When I was 17, the questions continued to catch me out, until I discovered that pressing Alt-X skipped them and took me straight to the game.

Could similar sets of questions be devised that only the young could answer correctly? If so, they are beyond the wit of this author (suggestions on a postcard, please). In the meantime, the best way to protect our children is to teach them how to spot an online fraud. As they enter the rabbit hole of misinformation that is the fully networked world, it will be a lesson that will last them a lifetime.