A man has been cleared of possessing indecent images of children on his company laptop after a court found that they had been placed there without his knowledge after it was infected with malware.

Michael Fiola, a 53 year-old investigator with the US Department of Industrial Accidents (DIA), was found not guilty after the defence and prosecution agreed that he had not intentionally downloaded or viewed the images.

Fiola was initially investigated in March 2007 after Verizon warned his employers that his phone bill was four times higher than it should have been.

The investigation found the images in his web page cache files and Fiola was fired and criminal charges were filed.

Computer forensics analyst Tami Loehrs examined the machine as part of the investigation and found that it was using corrupted antivirus software and was riddled with malware from a variety of sources. Loehrs described the treatment of Fiola as "horrific".

"As soon as you mention child pornography, everybody's senses go out the window," she told The Boston Globe.

"There is no evidence to support the claim that Michael Fiola was responsible for any of the pornographic activity."

Loehrs discovered that the computer was being used to store the images remotely, and investigators from the government agreed with her conclusions.

Fiola is now planning to sue the DIA for its handling of the case, maintaining that his life and reputation have been ruined.

Timothy Bradl, Fiola's attorney, said: "Imagine this scenario: your employer gives you a ticking time bomb full of child porn, and then you get fired, and then you get prosecuted as some kind of freak.

"This could happen to anybody who has a work laptop. Fiola is a 'hunt-and-peck' kind of computer guy. He can barely get on the internet."