Sven Jaschan has admitted writing Sasser on the first day of his trial.
In front of a court in Verden, Germany, the 19-year-old virus writer admitted to creating the worm which wreaked havoc worldwide through early 2004.
"Admitting his involvement was a sensible move by Sven Jaschan," said Graham Cluley, senior technology consultant at antivirus company Sophos. "The court is likely to respond with a lenient sentence on account of his age at the time of the offences, and because he has confessed his guilt. The court will now be interested in hearing evidence as to the impact of Jaschan's malware."
The hearing is taking place behind closed doors and is expected to finish this week. Katharina Kruetzfeldt, spokeswoman for the trial, revealed that Jaschan had admitted the charges, repeating his statement last year.
In December last year Jaschan stirred more controversy when German company Securepoint hired the teenager and created a spat between themselves and another German firm that objected to the hiring of virus writers.