Investigators in Sweden have questioned an unnamed person on suspicion of writing the Ganda worm, according to local reports.

The worm, which posed as a screensaver offering spy satellite photographs of Iraq, caused concern when it began to spread, albeit modestly, last week.

Torbjörn Ull, an IT crime specialist working for the Swedish police, is quoted as saying the suspect admitted involvement in writing the virus.

The identity of the suspect has not been disclosed.

Carole Theriault, anti-virus consultant at Sophos, believes messages in the virus itself may well have helped police identify their unnamed prime suspect.

The Ganda worm spread via email in either English or Swedish using a variety of email subject lines and message bodies. The worm appears to have been particularly successful in spreading in Sweden. Infected users in Sweden may have been lulled into a false sense of security when they received an email in their native language, rather than the English adopted by many viruses.

The worm, as usual, only affected Windows PCs.

More details of the Ganda worm are available in from Sophos? Web site, while MessageLabs records the worms modest progress across the Web here.

MessageLabs has blocked only 1050 instances of the worm since its appearance on March 16: barely one per cent of the number of times the messaging service firm blocked Klez over the same period.

Attention has been drawn to Ganda because of its war theme rather than the damage it causes, although MessageLabs says it is capable of taking out AV programs and causing some collateral damage on infected PCs. Finnish AV specialists F-Secure have a technical write up of the worm here. ®