Greater digital security is needed to counter the threat posed by Islamic State's (IS) use of social media, the head of the Security Intelligence Service (SIS) says.
Rebecca Kitteridge made the comment at a conference on digital identity and privacy in Wellington yesterday.
Ms Kitteridge told the conference the threat from IS is growing because of its efficient use of the internet.
"The internet overcomes geographic distance and enables communication between these susceptible people and those encouraging, radicalising and directing them.
"The internet, and especially social media, means it is very easy for these individuals to connect with others who share and strengthen their world view," she said.
The SIS had 51 domestic security warrants in force over the past year.
Ms Kitteridge said that was a miniscule percentage of the population under surveillance but the threat of domestic terrorism in this country was a growing concern.
"We've seen the consequences of ISIL's communication strategy and tactics being experienced in Paris, Belgium, Ottawa, Melbourne and Sydney where lives have been taken or threatened," she said.
But a former Australian privacy commissioner warned New Zealand not to introduce a similar security law to those in his country, which he said equated to massive but passive surveillance.
In Australia, the reaction to greater domestic security fears posed by the use of the internet was swift.
It passed contentious legislation earlier this year - the Metadata Retention Law.
Malcolm Crompton said New Zealand should be concerned, but Australia's law is not a solution.
He said the new Australian law works in a similar way to the Google Now information app - except that authorities will have access to a person's digital identity.
"It can see your habitual patterns by the activity of your digital devices, working out quickly where you work and where you live," he said.
Ms Kitteridge told the conference that about 30 percent of New Zealanders feared they were being watched, yet the SIS was interested in only 51 people out of a population of 4.5 million.
She told the audience to enjoy the freedom that the internet gives.
"You are free to click on whatever you want on your device, and you won't pop up on our system."
But another security consultant, Stephen Wilson, said authorities would have searched high and low to reach the watchlist of people they were monitoring.
"The spy agencies are collecting some information on almost everybody because they want to look for patterns, suspicious behaviour, the needle in the hay stack, and then they issue warrants.
"I'm OK with that as long as there is some independent oversight," he said.
Privacy Commissioner, John Edwards said the SIS did not have the resources for mass internet surveillance.
"They don't have the capacity to keep tabs on everyone and its not their mandate.
"The process they have to go through to get warrants for interception means they cannot just go chasing after someone for no reason," he said.
The conference, Enabling Digital Identity and Privacy in a Connected World, continues today.