The minister responsible for the country's spy agencies says they can't constantly monitor the internet to identify terror threats and instead rely on the public to raise the alarm.
A 27-year-old man has been charged with threatening to kill worshippers at Linwood Islamic Centre and Al Noor Mosque in Christchurch. He cannot be named for legal reasons.
Police said the man made the threat on 4chan, a website frequently used by extremists and white supremacists.
A cached version of the website shows a message board that details a plan to use car bombs to kill more people than in the 2019 shootings.
Security officials first became aware of the threat after they were alerted to it by a member of the public.
Minister Responsible for the GCSB and NZSIS Andrew Little told RNZ once the lead was provided, police and security services worked together to ensure the person was caught.
Little said the security services had to rely on tip-offs to pick up threats of this nature and did not monitor every New Zealander.
There are millions of posts on 4chan and other similar websites daily and they could not be monitored by the security agencies, he added.
"While I'm satisfied that the intelligence agencies have the capability and the means to be across the various threats that we face, in the end they operate like every other intelligence and security agency around the world on the basis of leads," Little said.
"They focus their work on persons of interest and on information that gives rise to the need for greater scrutiny. That happened in this case."
Little is also responsible for the government's implementation of the recommendations made in the 15 March Royal Commission report.
The lengthy report, released in December last year, painted a picture of under-resourced security agencies.
Asked whether under-resourcing was why the security agencies didn't become aware of this threat sooner, Little said that was not the case.
"The Royal Commission was very clear, it is not possible to monitor the internet. The Royal Commission was very clear that security and intelligence agencies operate off leads and their recommendations really focused on making sure that the whole community was aware of threats and felt confident reporting leads to the authorities," Little said.
RNZ
