The Wonderland Club's international membership is disturbingly exclusive.

Applicants must be sponsored by a member, be computer literate to communicate with other club members--and must have at least 10,000 photographs of child pornography.

In what was termed the biggest child pornography bust ever, the Customs Service announced Wednesday it was breaking up the Wonderland Club. More than 100 warrants were issued in 12 countries the day before, including 32 in the U.S., and arrests continued through Wednesday.

"They trade in the most vile child pornography imaginable, over the Internet," said Customs Commissioner Raymond Kelly in announcing the raids.

"The people who exploit children in these ways think they can hide in cyberspace. They're wrong," he said.

Cyberspace has become the venue of choice for traffickers in child pornography, customs officials say. The vast majority of child obscenity now flows into the U.S. through modems rather than seaports or airports.

"It makes it more difficult for law enforcement to investigate," Kelly said. "In the '70s and '80s, when (pornography) was in book form or commodity form, it was much easier."

Even in the abnormal world of child pornography, the Wonderland Club stood out. It had members in 14 countries, mostly in Western Europe, and sprawled across 22 states in the U.S., mostly in small towns or rural areas, according to law enforcement officials.

One of the warrants issued Tuesday was in southern Illinois for a resident of Glen Carbon.

"The Internet allows these things to sink deep into the fiber of the United States," said Gene Weinschenk, who heads the CyberSmuggling Center at the Customs Service.

The Wonderland Club's elite membership exchanged photos. Sometimes family members were shown molesting children; occasionally victims were as young as 18 months. Club members even transmitted live photos and videos in real time of sex acts with children.

The ring used a secret, highly restricted Internet chat room. It was set up in an area of cyberspace known as Internet Relay Chat, which allows discussion groups to carry on in complete anonymity and therefore to have graphic or incriminating discussions.

Secrecy was at a premium within the club, said customs officials. Members used an encryption system invented by the Soviet KGB to scramble its transmissions and make them harder to detect.

"This is a tight-knit group of people," Kelly said. "You had to have someone vouch for you. It was a very difficult process to get into the group."

Those arrested Wednesday were charged with possession of child pornography, which carries a penalty of up to 10 years in prison. Customs officials are still investigating whether they can charge some of the participants with more severe crimes, such as child sexual abuse.

The suspects' computers were seized so experts could seek evidence that they had been used for pornography.

Because some of the suspects might have been using their own children for the pornography, officials hope that in the process of making the arrests they will find some of the abused children.

Child advocates were enthusiastic about the widespread raid, praising the agents involved.

"They were under time constraints because they had children being exploited, so they had to work quickly and coordinate a worldwide takedown," said Ruben Rodriguez, director of the exploited child unit at the National Center for Missing and Exploited Children. "And you're dealing with the laws of many, many countries, which can be an obstacle."

The raids occurred in Australia, Austria, Belgium, Britain, Finland, France, Germany, Italy, Norway, Portugal, Sweden and the United States.

The customs investigation was sparked by a tip from British authorities investigating another child cyberporn ring. The customs initiative was dubbed Operation Cheshire Cat, in response to the ring's "Wonderland" title.

Agents did not go undercover or surreptitiously join the pornography club as part of their investigation. Rather, they used computer sleuthing methods that are rapidly becoming vital.

By watching the Internet activity around the chat room, agents determined the computer identities of the suspects.

Then they traced them through an electronic maze to figure out their actual identities.

"Agents tracked these people through cyberspace as they hid behind Internet providers, servers, and screen names," Kelly said.

Because of the Internet, child pornography trafficking has soared in the 1990s, said Rodriguez. It is impossible to pinpoint its magnitude.

"Can anybody tell you how big the problem is? No one can," Rodriguez said. "You have an anonymous medium."

Federal authorities have recently begun focusing more on child pornography on the Internet. In 1995, customs officials arrested 48 people on child pornography charges. So far in 1998, the number has nearly quadrupled to 183.

"I hope this sends a message," Rodriguez said. "It takes away the anonymity on the Internet. It shows that law enforcement will find you, even if you use encryption."