A Florida man faces up to ten years in federal prison and a quarter-million in fines, after pleading guilty to dropping adware onto unsuspecting users' computers for cash.

Botnet master Robert Matthew Bentley, 21, of Panama City, Florida, pled guilty to conspiracy to commit computer fraud and computer fraud charges. Bentley was one of eight bot net herders busted under Operation Bot Roast II, an anti-bot net and spammer campaign that was launched with participation from London Metro Police, the US Secret Service, US Federal Bureau of Investigation, Finland National Bureau of Investigation, and other agencies.

Having established a sophisticated network of hijacked bots that were taken over using adware, Bentley and several co-conspirators were paid about 0.15 euro ($0.25) for each PC on which they successfully dropped adware. The money came from what federal investigators are calling a "Western European-based operation" Dollar Revenue.

Bentley and company allegedly spread adware through web site smokedro.com and several IRC channels, and it appears all damages were to the software only, with no reported physical computer damage.

The botnet was established in October 2005 and was active for 13 months before companies and police agencies in December 2006 contacted the FBI for help. The London Metropolitan Police Computer Crime Unit ("The Met") requested assistance from the US Secret Service when representatives from at least two European companies reported unauthorized intrusions on their computer networks.

One company, Newell Rubbermaid, reported at least 100 of its computers were infected, costing it at least $150,000 to neutralize the adware. The company still says it is finding new infections it believes are tied to Bentley.

The first guilty plea related to Operation Bot Roast came after Robert Soloway, the "king of spam," pleaded guilty last week in a Seattle court to charges of mail and wire fraud, aggravated identity theft, and tax evasion. Soloway faces up to 26 years in federal prison and fines up to $625,000.

"The identification, indictment, and conviction of Bentley constitutes a significant success in a complex international investigation, and resulted from the outstanding cooperation of the many participating law enforcement agencies," US Attorney Greg Miller said in an official statement.

"The use of 'botnets' -- a series of computers covertly controlled by Bentley and his co-conspirators to accomplish the intrusion of victim computer systems -- is a major focus of computer-related criminal investigations worldwide."

Organizations and malicious users infect or hack computers often so they can have the ability to launch spam attacks or attack other vulnerable PCs. Commonly, a successful spam or adware attack forces companies to take their computer networks down and often times reinstall software, costing them valuable downtime.

Bentley was originally indicted by a grand jury in November 2007. He will be sentenced on Wednesday, May 28.