Trojan horse found responsible for child porn

A man accused of storing child pornography on his computer has been cleared after it emerged that his computer had been infected by a Trojan horse, which was responsible for transferring the images onto his PC.

Julian Green, 45, was taken into custody last October after police with a search warrant raided his house. He then spent a night in a police cell, nine days in Exeter prison and three months in a bail hostel. During this time, his ex-wife won custody of his seven year old daughter and possession of his house.

This is thought to be the second case in the UK where a "Trojan defence" has been used to clear someone of such an accusation. In April, a man from Reading was found not guilty of the crime after experts testified that a Trojan could have been responsible for the presence of 14 child porn images on his PC.

Trojan horses can be used to install a back door on a PC, allowing an attacker to freely access the computer. Using the back door, a malicious user can send pictures or other files to the victim's computer or use the infected machine to access illegal Web sites, while hiding the intruder's identity. Infected machines can be used for storing files without the knowledge of the computer's owner.

Kevin Hogan, senior manager at Symantec Security Response, told ZDNet UK that he has known Trojans to pretend to be a game, picture and even a Windows folder. "It is technically possible for a Trojan to set up someone's computer as a proxy machine. So you see a folder on your desktop, double click it and it executes."

According to Hogan, a Trojan back door can usually be dealt with by using an up-to-date antivirus software or a personal firewall.

Green told The Evening Standard that the experience wrecked his life because he was treated like a depraved sex fiend. "I had never been in trouble before. In cases like this it is not innocent until proved guilty, but the other way around," he said.

Green is reportedly planning on suing the police for compensation.