New Zealand's connections and involvements in the United States' mass surveillance network is set to be revealed tomorrow.

The New Zealand Herald, alongside Dirty Politics author Nicky Hager and other outlets, have prepared stories based on documents taken from the National Security Agency by whistleblower Edward Snowden.

According to Hager, the documents will focus on New Zealand's spying on other countries, saying "some of that won't be a surprise and some of it will be a great surprise."

Prime Minister John Key doesn't know what's going to be released but has advice for New Zealanders.

"Discount massively everything you hear from Nicky Hager," he said.

"He was wrong last time, he's wrong this time. His interests are his own self-serving interest not the interest of the country."

"I intend to sleep like an absolute baby tonight," he added. 

Prior to last year's Moment of Truth event, reporter Glenn Greenwald published stories in The Intercept detailing how New Zealand was working with the NSA to tap undersea internet cables in a project known as Speargun.

The Intercept claimed that these cables carry "the vast majority of internet traffic between New Zealand and the rest of the world, and mass collection from it would mark the greatest expansion of GCSB spying activities in decades." 

Snowden revelations: 

Spying on foreign leaders 
Edward Snowden revealed the United States had monitored phones of 35 world leaders, including German Chancellor Angela Merkel and Brazil's President Dilma Rousseff. Australia targeted the Indonesian President while Britain's spies were monitoring emails of politicians at two G20 meetings in London.

Cable tapping
The Five Eyes spy partners have tapped into the world's internet and telecoms cables, Snowden revealed, giving it the ability to suck up almost all the data which passes through them.

XKeyscore
The so-called "Google for spies" is a search tool which trawls the massive pool of data acquired by the NSA and its partners. It operates at 150 sites, according to one Snowden document, including one in New Zealand.

Mobile phone encryption
The US and UK hacked into the world's biggest sim card manufacturer, taking encryption keys. It gives the potential to bypass security and listen in on content passing across networks in dozens of countries.

Hack attacks
The NSA's Tailored Access Operations unit can hack info from protected computer systems and is able to install malicious software on computers and phones.