Aaron Caffrey, 19, claims that his computer was hijacked by two hackers known as Dry Ice and Friction using a Trojan horse to remotely control his PC without his knowledge.
Caffrey was arrested last year after US police traced a denial of service attack that crashed the Port of Houston's website in Texas to a computer at Caffrey's home in Shaftesbury, Dorset.
Giving evidence yesterday at Southwark Crown Court, Caffrey said he had seen evidence of Dry Ice and Friction's hacking ability in scripts for Zombies and Trojan Horses in a chatroom on a .tv domain that the two hackers had set up using stolen credit cards.
But the prosecution counsel said Caffrey had coded a Unicode exploit denial of service tool and put links to a compressed version of the file his own website under the banner "Allied Haxor Elite".
Caffrey said he put the hacking group name up just to annoy other hackers and said the files were just "resource scripts" that allowed people to change the font and type of text in chatrooms and add more visual features.
"If it [the script] was there, it didn't contain anything to do with denial of service and even if it did it wouldn't be illegal. It's perfectly legal to have one," he said.
An expert witness for the prosecution last week dismissed Caffrey's claims that his PC had been hijacked. The witness said there was no evidence of an attack and that it was technically impossible for a hacker to remove all traces of having planted or altered data on the computer.
When the prosecution put this to Caffrey again yesterday he said: "The technology exists and I can even explain how it works."
Caffrey has pleaded not guilty to unauthorised modifications of a computer contrary to Section 3 of the Computer Misuse Act 1990.
The case continues.
