Mr Aaron Caffrey walked free from court after being acquitted

Aaron Caffrey, 19, was accused of crashing systems at the port of Houston in Texas.

He had faced one charge at Southwark Crown Court of unauthorised modification of computer material.

But Mr Caffrey, of Fairlane, Shaftesbury, Dorset, was found not guilty by a jury on Friday.

Speaking after the verdict, he said he was "very angry" at the way he was "interpreted" and "treated" by the police.

Outside the court his barrister, Iain Ross, said: "He wishes to say that this ordeal has been a dark cloud hanging over him for the last two years.

"He had always insisted he was not guilty and that he was a victim of a criminal act rather than being a criminal himself."

During the trial it was claimed Mr Caffrey had perpetrated a complex crime, involving computer hacking, identity theft and fraudulent financial-market trading.

Attack script

Paul Addison prosecuting, told the jury Mr Caffrey hacked into the computer server at the port in order to target a female chatroom user called Bokkie, following an argument.

It was said in court they argued over anti-US remarks she had made.

I have hacked into computers legally for friends to test their server security because they asked me to but never illegally Aaron Caffrey Doubts cast over future hacker cases

Mr Caffrey, who suffers from a form of autism called Asperger's Syndrome, was said to be in love with an American girl called Jessica.

The court was told he named his computer after her and dedicated his "attack script" to her.

The attack saw scheduling computer systems at the port bombarded with thousands of electronic messages on 20 September, 2001.

It froze the port's web service, which contained vital data for shipping, mooring companies and support firms responsible for helping ships navigate in and out of the harbour.

Hackers and crackers

An investigation by US authorities traced the computer's internet provider number to a computer at Mr Caffrey's home.

But the teenager claimed an unidentified third party had planted the instructions for the attack script on his website without his knowledge.

He also criticised the authorities for not uncovering the virus during their investigation.

On the final day of the trial, Mr Caffrey admitted being part of a group of hackers called Allied Haxor Elite, but denied he had ever illegally hacked into a computer.

The teenager told the court that hackers operated legally, but that people who entered computer systems illegally were known as "crackers".