For many years people have accepted that having a spare Hotmail or Yahoo address is a good idea, primarily to discourage spam advertisers and maintain a certain level of privacy.

However, as the internet expands into chat, instant messaging and voicemail, the need for adopting new identities grows. When a female uses a chatroom, for instance, does she really want 10,000 men fantasising over her real features with the (admittedly remote) possibility that she might be recognised in real life? This might explain why so many female chatters and lonely hearts claim to be the spitting image of Buffy the Vampire Slayer. It also emphasises the good reasons for owning a fake digital passport.

Here is how you do it in five easy steps.

1. The Handle
All fake identities start with the name. Your name is what identifies and characterises your online presence, and has been twisted beyond recognition for years. For every genuinely Cute_Hot_Chick there are 100 20-stone brickies going by the same name.

Handles can be picked up at all the major portals (Yahoo, MSN, AOL, Lycos), although you may find that most of the obvious variations of your name have already been taken. Simply register for their free instant messenger service (IMS), most commonly Yahoo Messenger, IRC or MSN Passport, and choose your desired moniker. This also gives you a new online email address, which you should always use to field your mail from that particular service. It may be confusing juggling multiple mailboxes and identities, but it is a lot better than having your personal inbox flooded with porn and spam.

2. The picture
If you want to upload your real picture to portals, chatrooms and public briefcases, all well and good. However, having assumed a brave new handle, you might as well pick a matching picture. For instance, those who describe themselves as "a Tom Cruise lookalike" (ie short) will obviously need a jpeg to prove it. Try http://marina.fortunecity.com/shark/133/AvatarCollective.htm for celebrity mugshots or www.romanys realm.com for a wide selection of glamour pics. Alternatively, try the excellent www.uglypeople.com for a hilarious antidote to air-brushed good looks. Remember, the exception to the fake-picture rule is dating, where it can cause deep annoyance among fellow lonely hearts and greatly diminish the size of your post-bag.

3. Message and video
Most IMS now incorporate voicemail, voicechat and webcams. Why anyone would want to conceal their real voice is anyone's guess, but humorous voicemail messages can be downloaded from www.1st-comedy4phones-greetings.co.uk and text can be converted instantly into Stephen Hawking-style voicemail by downloading a freeware programme such as Talking Clipboard Sadly, the great man's intelligence cannot yet be downloaded, but voicemail is already beginning to replace text messages as an easy and cheap way of keeping in touch.

4. The 3D avatar
If you want to go the whole way, a JPeg of your face can be mapped on to a variety of virtual skeletons. The best known of these is Digimask, which requires two photos, one taken from the front, and the other taken in profile. Your first model is created free of charge, after that you have to earn credits.

Another fine example of a virtual community is www.cybernetworlds.com, which allows you to choose from a range of off-the-peg 3D avatars. Unfortunately, avatars cannot usually be used outside their host community, something future generations of instant messaging may correct.

5. Leaving the real world
Finally, once you have discovered the unreal you, there are alternate worlds galore to test them out in. From the fantasy roleplaying of Everquest to virtual communities such as Citizen X ( www. citizenx.com ) to free dating services such as the excellent Love@lycos, the fake ID allows you to be a little bolder.

Conclusion
Behind all the fun and games is a serious purpose. Websites that paste real faces on to pornographic images are already commonplace, and the dangers of persistent lonely hearts tracking you down is sadly also on the increase. Consequently, fake IDs, faces and addresses are probably no bad thing until you get to know your online friends better - indeed, the moment of swapping "real" photos is already becoming an important part of digital foreplay.

Enjoy it while it lasts.