The 21-year-old programmer from Schoenau in Germany who was accused of writing the Phatbot Trojan was released on bail on Friday after spending just one week in custody.
Phatbot, also known as Agobot, has caused concern among many security experts because it allows a single individual to control a vast network of computers, potentially as a means to attack commercial Web sites. The coder was captured last Friday, the same day that an 18-year-old man, also a resident of Germany, was arrested for creating the Sasser worm.
The man was released after instructions from the German public prosecutor's office. Authorities say they do not expect him to jump bail because his passport has been confiscated. He is required to check in regularly with the police to verify his whereabouts.
The preliminary investigation by the public prosecutor's office will decide if there is enough evidence to proceed.
The programmer, who claimed to have worked with a team of coders from all over Germany in order to create the Phatbot worm, was arrested after advice from US authorities.
CNET News.com's Rob Lemos and ETF's Lucy Holliday contributed to this report