A computer program that tries to delete files on handheld computers has been created as an "experiment" by a Swedish programmer.

The destructive program is thought to be the first written to do damage to the increasingly popular palmtop computers.

Anti-virus companies say few people are likely to be affected by the virus which does not replicate and has no means of spreading by itself.

But they warn that as handheld computers become more common, virus writers are likely to start targetting the devices.

The program is disguised as a piece of software that supposedly changes or "cracks" a version of a GameBoy emulator called Liberty, turning a free copy of the software into a registered version.

The destructive program, known as a "trojan", was reportedly created by a Swedish programmer to see if it could be done.

However, instead of letting owners of handheld computers play GameBoy games, it tries to delete all the files on the machine.

Handheld harm

Any handheld device running the Palm operating system could be caught out by the program. This includes machines made by Palm itself as well as HandSpring, Symbol, TRG, and Sony.

So far though, there is little evidence that anyone has lost data because of the program. Anti-virus companies say the fact that it has to be downloaded and has no way to replicate itself, makes it unlikely it will affect many people.

The program has now been removed from the web, making it even less likely to catch anyone out.

At the same time as the pernicious Palm program was being discovered, a Norwegian company was demonstrating how to briefly disable a mobile phone with a text message.

Many mobile phone operators use smart text messages to update the handsets of customers. The messages can give the phone a new ring tone or switch on services that used to be blocked.

But Norwegian company Web2Wap has accidentally discovered a smart message that disables all the buttons on a phone receiving it.

Unlike a virus the smart message will not do any damage to the phone or erase any information.

A spokesman for Nokia said it was sending engineers to Norway to investigate the discovery. He said currently Nokia cannot replicate the disabling smart message that Web2Wap claims to have found.

Any phone hit by the message will reset itself after 30-40 seconds and only a small number of its range of phones could be disabled by the message said the spokesman.