Once installed, the Trojan horse devices used premium rate “0190” phone numbers linked to an online adult website.
With the scam, Germany’s Deutsche Telekom handed over huge commissions to the two men, 31 and 35, who face nearly four years in jail.
But prosecutors failed to win a court order forcing them to repay $9.2 million to victims. Authorities in this northwestern city between Hanover and Dortmund also were seeking jail terms of five years apiece.
Earlier this year, two other persons suspected of aiding and abetting the defendants convicted of computer fraud received suspended jail terms.
The scale of the fraud prompted a rewiring of the German phone system to prevent future incidents.
“The German authorities have done well in bringing these offenders to justice,” said Graham Cluley, a senior technology consultant for Sophos, in a statement. “These hackers infected a staggering 100,000 PCs and forced them to dial a premium rate number to make them cold, hard cash.”