An Auckland computer hacker, who scammed hundreds of thousands of dollars and attracted the FBI to New Zealand, has been jailed for three years.

Tomasz Grygoruk, 22, was jailed on five charges of blackmail, document and computer fraud when he appeared in the High Court at Auckland yesterday.

Grygoruk spent five years and used an internet scam getting personal details from people to make A" cards. He then used the cards to withdraw up to $300,000.

The court heard he also got into the email account of an American teacher in Pennsylvania and tried to blackmail him, threatening to disclose details of a relationship with a student unless he was paid US$10,000 ($13,000). The relationship was not inappropriate.

Grygoruk had threatened to tell the teacher's local police and newspaper he was a paedophile who was romantically involved with the student.

The teacher called the FBI and an FBI agent pretended to be the teacher's accountant and later traced Grygoruk's New Zealand address.

The FBI also sent an agent to New Zealand last year to help with the case.

Over five years Grygoruk used trojan computer viruses that allowed him to access personal information on the internet from thousands of individuals.

He set up bank websites and sent thousands of unsolicited emails inviting individuals to provide personal details including credit card numbers and PIN numbers under the illusion they were being provided to the bank.

Using that information he created magnetic cards and got between $200,000 and $300,000 in cash from A" machines.

In the High Court at Auckland, Crown prosecutor Simon Mount said the offending was sophisticated and involved a large degree of planning.

However, he also said it was a mitigating factor that Grygoruk voluntarily went to the police to confess some of the computer scams that could otherwise have been undetected.

Justice Lyndon Stevens said home detention was not appropriate but added a rider that Grygoruk would greatly benefit from treatment for substance abuse and behavioural issues once he was released from jail.