A New Zealand teenager accused of involvement in an international cyber-crime ring which skimmed millions of dollars from bank accounts has been convicted of illegal computer hacking.

Owen Thor Walker, 18, allegedly led a group of hackers who used his programmes to send malicious software to and steal data from at least 1.3 million computers worldwide, resulting in losses of US$20 million (£10.1 million).

Mr Walker, who was arrested as part of an FBI investigation in December, yesterday pleaded guilty to six charges relating to using computers for illegal purposes.

Some of the crimes carry a maximum sentence of seven years in prison, but the judge who heard the case in court in Thames, south of Auckland, suggested that a prison sentence was unlikely.

Hackers frequently send out viruses and other malicious programmes via e-mail which infect the recipient's machine and allow the hacker to take control of it.

The computer then becomes part of a vast network of 'zombie' machines known as a 'botnet', which can be directed to attack other machines or steal personal details such as bank account and credit card information.

Mr Walker, who used the online name Akill, designed a virus which was undetectable by antivirus software, and made nearly NZ$40,000 (£15,750) selling it to other hackers, police said. The programme he wrote was "among the most advanced" investigators had encountered, they said.

So far eight others have previously been charged or convicted or had pleaded guilty as part of Operation Bot Roast II, which in this case involved the FBI working with New Zealand police as well as Dutch authorities to uncover the hacking network.

The 18-year-old is due to be sentenced on May 28.

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