A nationwide child exploitation ring shared hundreds of thousands of "abhorrent" images and videos, many showing children aged under 10, police say.
Australian Federal Police (AFP) officers from Child Protection Operations detected the group in January and have since charged 21 people and expect up to six more arrests.
The AFP also located one of the child victims depicted in the images and who was known to one of the offenders who produced, shared and accessed the images and videos.
The group operated via a peer-to-peer, file-sharing network that allowed them to access each other's computers to view images and videos made in Australia and overseas.
"They will look at other people's computers and basically cherry pick what they want in terms of imagery and (then) download," Detective Superintendent Todd Hunter told reporters on Friday in Sydney.
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At one location, officers seized 26 computer hard drives that each had the data capacity of 500 megabytes to 2 terabytes.
The alleged offenders used specific keyword searches to detect the file-sharing networks, AFP Cyber Crime Operations Commander Glen McEwen said, but anyone could have accessed the material.
"The material seized can only be described as abhorrent and personally disgusting," he told reporters.
About 80 officers were involved and the people charged were from every state and territory except South Australia and Tasmania.
They were from all walks of life and included one woman, which police considered unusual for this type of crime, and they ranged in age from 22 to 76. Most have been granted bail.
The offences carry a maximum sentence of 15 years and those who produced some of the material could also face child sex assault charges.
Two of the men arrested were from Perth including a 76-year-old from Nollamara in the city's northern suburbs who was charged with one count of accessing child exploitation material and two counts of possessing such material.
A 32-year-old from Swan View in Perth's east was charged with one count of accessing child exploitation material and one count of possessing such material.
