A COMPUTER virus inadvertently helped police to catch a paedophile who accessed thousands of child porn images.

Teesside Crown Court heard that a virus, in the form of a "keystroke logger" program, installed itself on Joseph Catterson's PC - recording every press of a button he made.

Catterson, who admitted 16 counts of making indecent images of children along with a further charge of possessing 1,486 indecent images, had attempted to cover up his tracks by using clean-up software wiping out his search details.

Dan Cordey, prosecuting, said Catterson's computer was seized when police visited his then home at The Orchard, Sedgefield, County Durham, on March 3, 2005.

He said that the case was unusual in that for the most part, the defendant's had covered his tracks on the computer well.

He said: "Records had been deleted in an attempt to hide any search for indecent images of children."

But Durham Police engaged Detective Constable Sharon Robson, a specialist computer crime investigator, to examine the computer hard drive and she found specific search terms used to hunt for child porn and traced these to the thumbnail images in question.

She also found the keystroke logger virus that, unbeknown to Catterson, had infected his PC.

Mr Cordey said: "This turned out to be of assistance to the investigation and made it clear what the defendant was doing."

Catterson, 44, now of William Street, Chester-le-Street, told police that he had wide ranging sexual interests, but did not involve children. He later changed his plea to guilty with the offences in question being committed between January 1, 2001, and March 4, 2005.

Catterson was given a three- year community rehabilitation order and made subject to a sexual prevention order which placed restrictions on his contact with children and access to computers. He was also told he would have to register his address with police for the next five years.

Paul Cross, mitigating, said Catterson, a heating engineer, had not sent the images to anybody else.

All but 50 were also of the lowest possible category when it came to their strength.

Judge Les Spittle said: "These are not victimless offences, the images you viewed were not pictures or diagrams.

"They were real children subject to this indignity and abuse in order that people can get some sort of pleasure or sexual titillation."

The computer and the images were forfeited and ordered to be destroyed.