National anti-spam and censorship compliance manager Steve O'Brien and team leader Jon Peacock have been there since the beginning.
"In those days a lot of it was boy love material predominantly. The area of concern then was Auckland," Mr O'Brien says.
"In a lot of cases it was commercial operators either pushing the boundaries of what was legally allowed or operating with a lack of knowledge," Mr Peacock adds.
One thing that hasn't changed, though, is the driving force behind the offending: the thrill the people get from the material.
And it's getting more depraved as technological barriers are broken.
Now anyone with a cellphone can deal in images of abuse - there's no need to make a video or even risk getting film developed by someone else.
Mr O'Brien says: "The offender has always wanted to operate in a protective, safe and secure environment. When the internet first came, the offender thought, 'I'm operating in my own home, I've pulled the blinds down and nobody can see me.' It was a naive understanding."
Mr Peacock: "Because the mechanisms of offending are so diverse we need to be agile enough to adapt. We need to be flexible enough that if we need to develop a solution we have the capability of doing so."
The unit's work has to stand up in court, making the stage of gathering forensic evidence important. Timing is also vital. If the unit raids a house, sometimes members have to move in quickly to prevent someone from deleting their "dirty laundry".
The unit is focused on New Zealand but is in constant contact with overseas authorities, swapping data.
It has been behind a few major scalps, too, such as "London John", who was found in a chatroom offering to broadcast live images of him abusing his daughter in late 2011.
"We started chatting," says another member of the unit who caught him and who cannot be identified.
"He was in the 'incest room'. He expressed an interest in sex with his daughter and then the conversation went from fairly mild to fairly explicit and hard-core quite quickly.
"We moved on to another chatroom, which was probably safer to be able to talk [in]."
There "London John" offered to livestream his abuse. British authorities were alerted and arrived at his house as his former partner was dropping off their daughter for the weekend.
"They found out potentially he was abusing his son as well, although that's not been confirmed."
Investigations revealed he made videos to order, having abused his 5-year-old daughter for about 19 months.
"He was quite sadistic in the way that he abused her as well," says the man who ended it. "London John" was jailed for 9-and-a-half years.
The unit also helped to uncover an international child-trafficking ring when it came across an organiser of child sex tours to Nepal, where an upfront fee would get someone to a sex party where they could pick girls aged from 10 to 17 to abuse.
Although the typical offender now is middle-aged, when the unit began it came across more young people.
"We almost put that down to the internet as a new area and youth were experimenting with boundaries," Mr O'Brien says.
"We found the majority of these weren't dedicated offenders like we find today. They've strayed into an area, we've caught them and put them on the straight and narrow. They didn't appear before courts in the majority of cases."
A lot of work goes into identifying offenders. It's not uncommon for the unit to call in a botanist or arborist to see where a particular plant grows or what season it grows in.
Images or videos are closely examined to see if there are any signs of dates or locations from newspapers, magazines, fashion trends, architecture, accents and dialects.
They see some horrendous stuff and fortunately the unit's team gets access to support if needed.
"What throws us is new material because that's a rich source for us, but what we're seeing these days is that new material is often very sadistic, violent. It can be very disturbing," Mr O'Brien says.
"We have found that text files are very hard to deal with, if you get seven [files] on how to rape a 5-year-old, which go into explicit detail. That can create a longer-lasting impression than seeing a ... single image."
Surprisingly, some offenders are relieved to be caught and get help. "They know they are participating in a really evil act - that the victims are real children. Some want to be stopped."
The unit is still on the heels of those who don't.
Child abuse images and other objectionable material can be reported to the Department of Internal Affairs' censorship and compliance unit at censorship@dia.govt.nz or on (09) 836-8605, (04) 495-9383 or (03) 339-5479.
Tape-swapper busted through wrong address
Not every scheme involves high-level encryption or guarded chatrooms.
One New Plymouth man was busted sending a VHS tape of abuse to the wrong address when swapping objectionable videos with others.
When his house was raided, an unsent letter to the correct address was found lying on a table.
"Sorry for the balls-up," it reads.
"I'm tossing up if I should write to that last address that I sent your tape to or whether I should just let it go. Hopefully they aren't stuck-up people who have maybe put it in the hands of the police."
The man said he had put plenty of stuff his pen pal would like on the latest VHS tape and wrote a list of subjects he had for future videos.
The person who wrongly received the tape called the authorities and the game was up.
