News websites Stuff and RNZ have revealed they were the target of a cyber attack but say it was unsuccessful and their sites remain secure.

Stuff said it contacted the GCSB who gave it advice around protections and urged the company to contact other media outlets to let them know so they could be on the look out.

A spokesperson for Stuff said it was a Distributed Denial of Service attack but was successfully defended and the website was back to "business as usual".

A second media outlet - RNZ - has confirmed it's been the target of cyber attack in the last 24 hours.

RNZ says it understands it may have been by the same group that has been targeting the New Zealand Stock Exchange and is currently investigating.

A spokesperson said there was more than one attack, but the RNZ site remained secure and the audience was not affected.

TVNZ and Mediaworks said their sites had not been the target of any attacks.

Māori TV and NZME have been approached for comment.

AUT computer science professor Dave Parry told RNZ the attackers could be targeting media companies simply for publicity.

"The people that run the attacks are effectively subcontractors or independent contractors compared to the criminal gangs who are running the extortion side of it.

"So they're going out saying 'look, use us to do your extortion because look, we're really good and we can point it - we've taken this website down, we've done this so we're the people you should use'," he said.

The National Cyber Security Centre released advice for New Zealand entities today on preparing for an attack, based on information from the Australian Cyber Security Centre.

The information advised entities to contact internet service providers, among a long list of other recommendations.

The advice can be found here.