In an operation code-named "Mikado," police in Magdeburg searched the Internet over a six-month period for pornographic images of children and sought to identify those who swapped them. The hunt included the biggest search of credit card data in Germany, involving basically all of this country's more than 22 million cardholders.

Torsten Meyer, the operation's chief investigator at the Saxon-Anhalt state crime office, praised what he described as unprecedented cooperation from German banks and financial institutions.

"We've used an entirely new method of investigating this crime and all financial institutions here have been very forthcoming and cooperative in it," Meyer said on Tuesday. "We've been able to arrest 322 suspects in all of Germany, most of them rather affluent people who paid for the incriminating material with their credit cards."

Credit card companies filtered accounts

The suspected pedophiles could be identified because their credit cards were regularly charged the monthly sum of $79.99 (61 euros) or because they transferred the amount to a certain bank account. The fee gave them access to a child pornography Web site run from the Philippines. Over the past week, police also searched the homes and offices of the suspects, seizing computers, videotapes and compact discs.

In the postwar era, Germans showed great reluctance in allowing access to their personal information, and Germany subsequently has passed strict data protection laws. It appears, however, that resistance has begun to waver. A grass roots movement agitated against a nationwide census 20 years ago but more than three-quarters of Germans now have no qualms about responding to such a head count, the Süddeutsche Zeitung newspaper wrote on Wednesday.

Dragnet searches questionable

Saxony-Anhalt's chief prosecutor, Peter Vogt, said he didn't see any data protection problems in how the investigation was conducted.

"The police didn't have access to the data from 20 million credit cards," he told the tageszeitung newspaper. "It only received the data of 322 suspects from the credit card companies. They carried out the matching of the data themselves."

But others were alarmed by the credit card companies working with the police.

"The voluntary release of such data is highly questionable, for here, in principle, dragnet searches are simply outsourced to private firms," said Hartmut Kilger, head of the German lawyers association DAV in an interview with Reutlinger General-Anzeiger newspaper.

Schleswig-Holstein's top data protection authority, Thilo Weichert, however, defended the operation. "What was employed here is a classic method of investigation that can't be legally objected to."

But he added that there were "numerous possibilities for state prosecutors to get access to data in the field of banking and finance, which are highly problematic," including dragnet searches. "There, positive characteristics that indicate a suspect are not searched for alone, but also characteristics with which one can only engage in speculation."

The investigation -- which was started after a tip-off from a German television show whose viewers brought the child porn ring to their attention -- and its success recalled a case three years ago when investigators in Magdeburg led a global investigation against child pornography. At the time some 26,000 suspects in 166 countries were arrested on the basis of evidence gathered by the German specialists.

Struggle against windmills

Investigator Meyer admitted that fighting child pornography was a struggle against windmills in spite of the recent successes.

"We've been able to increase the pressure on pedophiles in recent years, but the deeper we look the bigger the magnitude of this crime appears to get," he said.

In Germany, the depiction of sexual acts by anyone under the age of 14 is considered child pornography. In the United States, in comparison, the age limit is 18. Distribution of child pornography in Germany carries a prison term of two to five years, while possessing such material means a maximum penalty of one year.

Meyer said that about 76 percent of child pornography cases are eventually solved. But, he added, a huge number remain undetected, as child pornography is a rapidly growing market in the Internet era.