A 21-year-old German man who was arrested and has admitted to creating the Trojan horse programs Agobot and Phatbot is not connected to Sven Jaschan, the author of the Sasser internet worm, a police spokesman said.
German police arrested the man on Friday in the southern German town of Waldshut and charged him under the country's computer sabotage law for attacks on computers in Germany, the UK and the US linked to Agobot and Phatbot.
Five other men were also charged in connection to the so-called Trojan programs, but there is no link to the arrest of 18-year-old Jaschan in connection with the Sasser Internet worm, said Horst Haug, a spokesman for the State Bureau of Investigation in Baden-Württemberg.
Authorities arrested the Phatbot author, a "self-taught" hacker, following tips in recent weeks from the FBI, Haug said. Police searched the suspect's home and seized computer hardware, software and documents.
Agobot is a Trojan horse program that surreptitiously runs on computers running Microsoft Windows, providing malicious hackers with secret access to the compromised system. Since first appearing in October 2002, hundreds of versions of Agobot have been detected, including variants called Gaobot, Phatbot, and Polybot.
The computer code for Agobot circulates widely on the internet, and may have been modified by countless individuals with access to it, said Mikko Hyppönen, manager of antivirus research at F-Secure.
Despite that, German authorities believe they have the original author of the Trojan, Haug said.
"He confessed to being the original author. He said he created both Agobot and Phatbot," he said.
Two other Waldshut men was also arrested on Friday in connection with the Agobot Trojan. Arrests were also made in Bavaria, Lower Saxony and Hamburg in the case, Haug said. The men are believed to work together to make Trojan horse programs and "other viruses", Haug said.
Information provided to the authorities leading to the Sasser arrest came from Microsoft rather than the FBI, and German authorities do not believe the two groups of malicious code writers knew each other or worked together, Haug said.
Before the arrests, however, officials were unsure whether the groups communicated with each other, and timed their arrests in the two cases to prevent crucial evidence from being destroyed, Haug said.
German police are analysing the information seized in the arrests on Friday, but cannot identify any of the suspects they have arrested, or describe the evidence against them, he said.
F-Secure has provided information to authorities on Agobot and Phatbot before, including the IRC (Internet Relay Chat) logs files containing user names and the IP (Internet Protocol) addresses of individuals who were selling customised versions of the Trojan horse program online, Hyppönen said.
The capture of the original Agobot author will increase the pressure on others who create malicious programs. However, the availability of the Agobot and Phatbot source code make it almost certain that new versions of the Trojan will continue to appear.
Paul Roberts writes for IDG News Service