A Christchurch sexual abuse prevention organisation is warning youngsters that they be in trouble with the law if they put intimate photos of themselves online.

Police are investigating after an online predator set up a Facebook profile posing as a Christchurch Girls High School student, called Ella Jamieson.

The imposter sent the boys sexually explicit videos and photos, and encouraged males as young as 13 to send nude selfies of themselves to the account.

Stop Chief Executive Don Mortensen said as close to home as Australia, young people have been prosecuted for publishing objectionable material online.

"I'm not aware in New Zealand of a case where this has happened but potentially it is breaking the law and people could be charged. Now a young person would not even have any idea of that."

Mr Mortensen said youngsters need to appreciate how much control they have over images posted online.

"There is a need for young people to realise that once are posted onto social media they lose total control of what those images are going to be used for."

It's becoming increasingly acceptable among young people for them to share sexual images of themselves, Mr Mortensen said.

"I don't think young people think beyond the actual act and excitement of sending a sexual image of themselves in anticipation of getting a sexual image back."

Christchurch Boy's High School Principal Nic Hill said it has classes for its students around the issues of digital citizenship and students digital footprint.

"It's education for the world our boys are going into. We can not avoid this stuff."

He said it teaches about the legal and ethical issues around what they put on the internet.

"There's lots of great stuff about the internet. There's some dangers as well and we shouldn't hide from it."

Police say the Online Child Exploitation Agency of New Zealand contacted Facebook in September regarding the account.

Police have confirmed they've received one complaint, but want to hear from an other victims.

They are also encouraging youngsters to remember that offenders often use fake identities, pictures they find online and background stories which have worked for them in the past.