Australian police on Wednesday said they have busted an international pedophilia network stretching from Australia to the United States and Europe and comprised of 2,500 "clients" who traded images of children being brutally sexually abused.

Authorities in Australia conducted raids and arrests on Feb. 29 not only in Australia and the U.S. but also in Britain and Germany, according to Reuters. Work on the sting — coordinated by the FBI and called Operation Achilles — has been ongoing since January 2006.

More than 40 children have been rescued and 22 members of the network been taken into custody as part of the operation, Reuters reported. The pedophilia ring had customers in at least 19 countries, and police confiscated thousands of videos, photos and computers in the bust.

"It will be alleged that the network traded images depicting the violent sexual abuse of children globally, including having children sexually abused live and on demand for the benefit of its members," police in the Australian state of Queensland said in a statement, according to Reuters.

Four pedophilia Web sites have been shut down, and more than 100 people have been arrested for allegedly buying material depicting sex with children, according to Reuters.

"It has been the most significant infiltration of an international child exploitation network by a law enforcement agency anywhere in the world," said Queensland police superintendent Peter Crawford from the state sexual crimes squad.

One of the network's members, 47-year-old James Freeman, was among the 12 Americans indicted last week in the investigation that ultimately charged 22 people with participating and intentionally blocking police from looking into it.

Freeman, of Santa Rosa Beach, Fla., posted two folders online to express gratitude for being accepted into the ring: one labeled "mild," the other "wild."

"All I can say is that they are worth the download," wrote Freeman, known in the global porn ring as "Mystikal," according to court documents. "My thanks to you and all the others that together make this the greatest group of pedos ever to gather in one place."

In all, more than 400,000 pictures, video files and other images showing children engaged in sexual behavior were produced, advertised, traded and distributed globally in the online pornography ring, according to U.S. and international authorities. The sting, which started in Australia, also netted accused pornographers in England, Canada and Germany.

Some victims were as young as 5 years old. Others were preyed upon for innocent characteristics such as wearing their hair in pigtails.

Authorities won't say how they eventually broke through several layers of encryption, background checks and other security measures the pornographers used to protect their online user group from being accessed.

The highly sophisticated porn ring was run like a business, FBI Executive Assistant Director J. Stephen Tidwell said Tuesday, with the lewd images used as currency instead of cash.

"This is beyond a quantum exponential leap for us to see folks that have gone to this much trouble to produce this kind of volume of horrific exploitation of children," Tidwell said in an interview. "But with 400,000 [images] we're going to be at this for years, trying to find the victims."

Australian investigators discovered the ring and infiltrated it under cover in January 2006, said Ross Barnett, detective chief superintendent with the Queensland Police Service. Those who gained access to the online forum first had to pass a series of what Tidwell called "various benchmarks and bars to get over to get into their group."

"From our perspective, it's definitely the largest and most sophisticated and disciplined group that we have ever seen operating in this environment," Barnett said.

When the investigation started two years ago, Australian police intercepted a number of commercially produced videos showing a Belgian man molesting two young girls, according to Reuters. The videos then were shared with authorities in France, Germany, the Netherlands, Belgium and Austria. The man was nabbed and the children recovered, Reuters reported.

A 35-count indictment unsealed Friday in U.S. District Court in Pensacola, Fla., details conversations among the 12 men accused of trading and advertising the pornography. Two other Americans also were arrested in connection with the ring but not included in the indictment.

The men were charged in 11 states: California, Connecticut, Florida, Idaho, Indiana, North Carolina, Oregon, Pennsylvania, Texas, Virginia and Washington. They all used aliases, such as "Box of Rocks," "Crazy Horse," "Lizzard" and "Pickleman."

In one example cited in the indictment, 54-year-old Raymond Roy of San Juan Capistrano, Calif., posted videos of Thai children "to give everyone something to do for an afternoon."

"This one may offend here, so a word of caution, these girls are heavily drugged," Roy, known as "Nimo," wrote on July 10, 2007, according to the court documents. "Not much action to speak of, the girls are [sic] to [expletive deleted] up to move, or resist. Three girls, the first one being the youngest, around 8 or 9 yo."

"Yo" stands for "years old."

The 12 men were charged with engaging in a child exploitation enterprise; illegally posting notices seeking to receive, exchange and distribute child porn across state lines; and obstructing of justice.

Several also were charged with producing the pornography — meaning they had contact with the children who were exploited, Tidwell said.

The investigation, which is continuing, is the latest product of the FBI's "Innocent Images" task force that stemmed from a 1993 child pornography case. The task force has arrested more than 9,400 suspects since 2004 and is made up of international investigators working in the United States from an FBI command center in suburban Maryland.

Noting the sophisticated process the porn ring used to bar police, Tidwell compared the growing number of child pornography crimes to that of cocaine dealers, terrorists and the Mafia.

"If they had good operational security, that's a bad thing for us," Tidwell said. "When you've got that, you've got a real challenge for law enforcement."

The Associated Press contributed to this report.