The German teenager who allegedly wrote the Sasser and Netsky computer worms has been charged.

Sven Jaschan, now 18, was arrested in May this year at his parents' home in Waffensen, North Germany.

He has now been charged with computer sabotage, which carries a maximum five-year jail term.

Jaschan was caught after police received tip-offs from informants after Microsoft offered a $250,000 reward for information leading to a conviction.

Graham Cluley, senior technology consultant at security company Sophos, said in a statement: "The Netsky and Sasser worms accounted for over 70 per cent of all virus infections in the first half of 2004.

"They were tremendously successful at spreading and a significant and costly nuisance for many companies and home computers worldwide.

"However, it seems that the number of infection reports to the police are just the tip of the iceberg. These were, without doubt, two of the biggest computer virus outbreaks of all time."