It's hard to know how much child pornography is in New Zealand, Customs' operations manager of investigations says, in the wake of a bust in New Zealand.
Stephen Waugh told The AM Show a lot of child abuse images are hosted on parts of the internet regular Kiwis would not know about.
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Images would sit on the dark web, on platforms specifically made for child abuse.
"That's say 95 percent of what we know as the internet, 5 percent being the clear net, so it's actually difficult to measure how big the problem is."
Customs covers the digital and physical border and works with a variety of partner agencies to investigate child pornography.
On Tuesday it revealed two New Zealand men had been arrested and charged in relation to child sexual abuse images.
Waugh said he would not be able to say how many children are being exploited, but his team goes to great lengths to find them.
That means quite often investigators are forced to look at images to assess their subject matter.
"You have to know the material you're looking at [to know] that it actually is what we call an objectionable publication or child abuse material.
"So a lot of time is spent viewing the material to ensure we are looking at the right thing and then from there our focus is always victim identification. That's the primary focus for all the agencies involved in this work. "
Once a victim is identified the agencies work to rescue them, which Waugh said was always the priority, followed by finding the people creating the material.
He said there are systems in place to reduce the mental load on staff forced to wade through the images. Customs uses software to sift out already known images from the ones needing investigation.
"We have to look after our staff and we invest in psych sessions for them to make sure that they are coping themselves, we have a network within our own partner agencies within New Zealand that we work between and sort of support each other.
"The team environment as well, the team environment is very important, if you've got that environment that supports the team, promotes them along, it mitigates a lot of those risks and the guys who do the work are very important.''