It all started in the French city of Lyons eight months ago. Stunned Australian Federal Police were presented with computer disks with excruciating details of the internet child porn obsessions of up to 500 Australians.

The international headquarters of Interpol is in Lyons. It was there that US investigators revealed the fruits of their investigation into a lucrative racket run from the former Soviet republic of Belarus. By then the writing was on the wall for the international network of porn sites uncovered in the lead-up to this week's crackdown on internet child abuse.

The previous month, US Attorney-General John Ashcroft had revealed the existence of Operation Falcon and the indictment of porn website company Regpay, a company operating from Belarus, and the US firm, Connections USA.

Regpay processed subscriptions for third-party internet websites, while Connections USA provided Regpay with credit card processing services for those subscriptions.

"Regpay allegedly processed nearly US$3 million ($A4.1 million) in subscription fees by persons seeking pornography - much of it being child pornography," Mr Ashcroft said.

The beneficiaries were Russian organised crime groups.

It is possible for a determined or even casual researcher to find all manner of objectionable material on the internet, including child porn. But the worst of it now appears to be kept well away from casual perusal and available only on a pay-per-view or subscription basis, using credit card details.

And it appears to be those credit card details that enabled Australian investigators to zero in on homes across Australia. More than 200 Australians already face charges following the execution of some 400 search warrants last week.

Further arrests and charges are expected, with Federal Police Commissioner Mick Keelty saying more than 500 Australians could be implicated.

Much remains to be revealed about just how the investigators' inquiry came together. It is known that US and probably Australian investigators trawled the internet for illegal material and presumably bought access to pay sites, gathering evidence in the guise of paying punters.

Operation Falcon was headed by the US Customs Service, whose lead investigator, Special Agent Kyle Hutchins, said that it uncovered 95,000 leads from one Belarus company - presumably Regpay - with most pointing back to the US. With the US end of the investigation well under way, they were then able to begin the Australian inquiry at Lyons with AFP liaison officers.

The operation was led by the Canberra-based Australian High Tech Crime Centre within the AFP. Officers liaised with state and territory police forces who conducted raids, seized computers and interviewed and charged suspects.

It appears to have been touch-and-go as to whether police could finalise their inquiries and searches before the news broke. Many media organisations apparently sniffed out that a major inquiry was under way but agreed to hold off.

The first details emerged on Wednesday night but the stunning magnitude of the operation, codenamed Operation Auxin, only emerged at media conferences by the AFP and state and territory police on Thursday.

The head of the Australian High Tech Crime Centre, Agent Mike Phelan, said police executed more than 400 search warrants in the previous week, charging more than 150 people. By late Friday afternoon, that figure was well out of date. By yesterday it exceeded 200, with more arrests expected. "Police have seized in excess of 2 million child pornographic images and this has included some persons having possession of one maybe two images up to those who have possessed full-image libraries of in excess of 250,000 images collected over three decades," he said.

Police also revealed they had uncovered home studios and photographic equipment used for production of child porn.

The array of charges revealed that those implicated may have done more than hoard and view images. Some were charged with rape and sexual assault while one man was charged with child-sex tourism.

- AAP