An increasing number of New Zealand women are heading to Iraq and Syria, SIS director Rebecca Kitteridge told the intelligence and security committee today at Parliament.
But she did not know whether they were going as "jihadi brides" to fight themselves or to support Isis fighters.
"What has changed over the last year is that the issue of New Zealand women travelling to Iraq and Syria wasn't something we have seen previously or been aware of previously," she said.
Asked by Prime Minister John Key if they were "jihadi brides" she said: "Presumably. It is difficult to see what they do when they go. We definitely have intelligence that they went.
Whether they are going to fight or whether they are going to support other fighters is not clear but it is a real concern that they would go at all."
Speaking to reporters later she would not quantify the number but confirmed the number was less than a dozen.
She would not comment on whether had any had returned to New Zealand.
She said the extent to which the SIS knew about any of them returning "of course we would maintain an interest in those people" but she said the SIS did not know about every single person.
"Obviously we would be concerned with whatever they are doing in a war zone of that kind.
"There would be really significant concern about what they are being exposed to, the conditions that they are, their ability to get away if they want to or how heavily radicalized or exposed to acts of barbarism they might be seeing.
"For a whole range of reasons it is a real concern to us."
Ms Kitteridge offered her remarks in her initial presentation then elaborated on them when Mr Key asked about the type of people that the SIS watched as a security risk.
"They may have other problems in their life," she said.
"It's not your kind of average person who's going out to work, or happily married or raising their kids.
"I would say there is a pattern of people who seem kind of disengaged in some way with productive life."
There were a range of age and a range of backgrounds - "quite a diversity of people actually."
Meanwhile, Mr Key questioned whether that a proposal he has previously rejected - attaching the Cortex cyber security programme to the Southern Cross internet cable linking New Zealand to Australia and the United States - should be revisited to give wider cyber protection to New Zealand companies.
He made the suggestion while questioning the acting director of the Government Communications Security Bureau, Una Jagose, who gave a detailed speech recently about Cortex as part of a new policy of openness in the bureau.
Mr Key said he had canned the original proposal because of the potential anxiety of it being seen as mass surveillance but he asked if an argument could be made, with enough public debate for it happen to protect smaller companies.
At present, the GCSB uses Cortex to mount cyber defence on Government agencies and strategically important private companies - and only with their permission.
Ms Jagose said the "hard ground work" by the GCSB needed to be done to be more open about the GCSB's cyber defence work.
She acknowledged the possible anxiety over "mass surveillance."
"We needed to have that maturing of the bureau and of the public to understand the threat and what we are doing about it. But one of our great advantages as a country is that we are small and we are surrounded by water and we have limited inputs for the international internet traffic to come.
"That is an opportunity for the future, I would say, that this country should think about very seriously because there is an opportunity to protect everybody, not just Cortex customers.
"On a future day, we might have that discussion again."
She said that in her engagement with boards and executive teams, she was asked quite often why the GCSB was not doing cyber defence for everybody.
"I think it is a question that will be asked of Governments in the future."