Prime Minister Jacinda Ardern says efforts to eliminate the banned footage of the Christchurch terror attack are still ongoing two years on.
It comes as an intelligence expert urges New Zealand agencies to not just depend on the public to monitor online extremism.
Monday marks two years since the Christchurch mosque attacks, where gunman Brenton Tarrant stormed Christchurch's Al Noor and Linwood mosques, opening fire during Friday prayers and killing 51 people.
According to a Royal Commission of Inquiry report into the attacks, released late last year, the gunman started using the online platform 4chan, often used for hate speech, from age 14. The Royal Commission believed exposure to such content contributed to his actions on March 15.
Earlier this month, a 27-year-old man was arrested and remanded in custody for making death threats against Linwood and Al Noor Mosque worshippers on that same online platform. Authorities were notified by a member of the public about the 4chan threats.
Two years on from the mosque shootings, intelligence expert Paul Buchanan told Newshub that presents a problem.
"The [GCSB and NZSIS] Minister had to admit that they got a tip-off and that they're very dependent on leads - that is of concern because at this stage of the game, two years after March 15, they should not be dependent on leads from the public when it comes to countering extremist threats of any sort."
It was notable, however, that agencies acted immediately after receiving the most-recent tip-off, Buchanan says.
He says New Zealand intelligence agencies had discounted the threat of white supremacists before March 15.
But Buchanan says there's more to be done. After the terror attack, which was live-streamed by the gunman on social media, Ardern established the Christchurch Call, a voluntary commitment from governments and online platforms intended to thwart terrorist and violent extremist content online.
But Buchanan describes those voluntary commitments as "empty".
"With all the resourcing that has gone to New Zealand's intelligence agencies, including dedicated units whose sole focus is to monitor social media for extremism - they did not discover this individual on an open forum.
"Instead, it took volunteers - activists who are unpaid - doing it out of the goodness of their heart to locate this individual and then alert the authorities.
"One has to wonder what on earth the intelligence agencies and the police are doing with the millions of dollars in resources they've been allocated as a result of March 15.
"The other problem is that although the Christchurch Call was made within a month or two after March 15 - it turns out that was an empty promise."
Buchanan says people still have open access websites commonly used by extremists - such as 4chan.
"Voluntary compliance does not appear to be working."
Appearing on The AM Show, Ardern conceded only some websites are listening to the Government's pleas to take down the gunman's footage.
"There are some who, of course, do not and that is the issue there," she told host Duncan Garner on Monday. "That is an ongoing challenge that we will continue to confront and continue to address.
"It should not be available anymore. Of course, it is illegal in New Zealand - but we have people that operate on the dark web and so it is a very complex area."
Minister Responsible for the GCSB and NZSIS Andrew Little told Newshub they are focussed on their mission to keep New Zealand safe.
"However they do not have either the legal mandate or the social licence, to carry out mass surveillance of the internet.
"There are tools for identifying particular activity on the internet which can be freely used by the public, however similar activity by the intelligence agencies is subject to strict legal controls.
"This activity must be necessary and proportionate, be conducted in accordance with the law, and is subject to ethical and privacy considerations."