Megaupload boss Kim Dotcom Thursday revealed plans to relaunch his file-sharing empire in January on the anniversary of his arrest in New Zealand on online piracy charges.

Dotcom is free on bail but still fighting extradition to the United States following a raid on his Auckland mansion on January 20, when New Zealand police arrested him as part of a major US investigation into alleged copyright theft and shut down his website Megaupload.

The 38-year-old German national announced on Twitter his plans to launch a new service called Mega, saying a teaser website had received millions of hits in just a few hours.

"One thing is sure: The world wants MEGA!," he tweeted.

Details of the planned service were scarce but the site promises to use state-of-the-art encryption methods that mean only users, not the site's administrators, know what they are uploading.

That would theoretically stop authorities from accusing administrators of knowingly aiding online piracy, the central allegation facing Dotcom.

At its peak Megaupload had attracted about four per cent of the world's internet traffic or 50 million hits a day, according to the US Department of Justice.

Dotcom is due to face a court hearing in March next year which will determine if US authorities can extradite him and three co-accused on charges of money laundering, racketeering, fraud and online copyright theft.

He faces up to 20 years jail if convicted in a US court.

The FBI and US Justice Department allege Megaupload sites netted more than $175 million in criminal proceeds and cost copyright owners more than $500 million by offering pirated copies of movies, TV shows and other content.

In September New Zealand secret agents were deemed to have acted "unlawfully" in the way in which they monitored Dotcom in the lead up to his arrest.