A young Wellington man with "mad computer skills" made a stupid mistake when he set up a "dark net" website to help him buy drugs, a judge has said.

James Jordan Winstanley, 22, also set up a Facebook page that led to the Vic Underworld site, which users then had to be invited to use.

However, Wellington District Court was told on Thursday that there was no evidence he supplied any drugs, and a police search of his home found no drugs.

Judge Bill Hastings said Winstanley did not have a formal diagnosis of autism, but it was clear he had "social deficits", and had in the past used prescribed medication for himself and others.

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"You are an intelligent young person with mad computer skills who also has certain social deficits which you have taken significant steps to overcome," the judge said.

"You made a stupid mistake when you set up this website."

The "dark net" is the backroom of the internet, where sites such as online drugs supermarket the Silk Road are hidden behind encryption systems. Sites are considered to be on the dark web if they can be accessed only by using special networks, designed to give visitors some degree of anonymity.

Winstanley's lawyer James Elliott said his client set up Vic Underworld to help him buy drugs, rather than use it as a marketplace. Winstanley knew no other way of getting drugs, and turned to what he did know, which was information technology.

He posted on the site using fake identities, to make it seem better used than it was.

Facebook took down the initial page, but Winstanley put up two more. The judge said this showed defiance and persistence.

He was caught as part of Operation Hyperion, in which police and Customs in co-ordination with international agencies targeted the buyers and sellers of illegal drugs.

He pleaded guilty to three charges of offering to supply MDMA, codeine and cannabis between May and October 2015.

Hastings told Winstanley he had come to his "day of reckoning", and sentenced him to four months' community detention and six months' supervision.