It comes as a warning from intelligence expert Paul Buchanan, who says a ban on the website 4chan is not foolproof, after a threat aimed at two Christchurch mosques was posted on the site this week.
A 27-year-old man was arrested on Thursday and appeared in court on Friday charged with threatening to kill worshippers at Linwood Islamic Center and Al Noor Mosque in Christchurch.
Police allege he made the threats on 4chan, a website frequently used by extremists and white supremacists.
Local internet service providers banned 4chan and the related 8chan, after the March 15 terror attacks.
But Buchanan said there are still problems.
"The bans instituted by the internet providers here in New Zealand is not sufficient when it comes to extremists communicating with each other."
Buchanan said New Zealand's intelligence agencies, the SIS (New Zealand Security Intelligence Service) and the GCSB (Government Communications Security Bureau) should take that as a "matter of priority concern".
Buchanan said he is pleased police are not ignoring such online threats.
He said although the police were alerted by members of the public, officers did well to act fast.
Buchanan said it was not concerning police did not sight the threats sooner, because at least they acted swiftly to arrest the man accused of making them.
Minister Responsible for the GCSB and NZSIS Andrew Little earlier told RNZ that security services cannot constantly monitor the internet to identify terror threats and had to rely on tip-offs to pick up threats of this nature.