Now, a group of 18 financial giants are embarking on a major effort to help federal agents follow the money.

"The credit-card system is one of the keys," said U.S. Sen. Richard Shelby, R-Ala. "It’s all about money, money, money."

Shelby originated the idea that eventually became the Financial Coalition Against Child Pornography. Founding members of the coalition include Visa, MasterCard, American Express, Discover Financial Services, America Online, Bank of America, Chase, Citigroup, e-gold, First Data Corporation, First National Bank of Omaha, Microsoft, PayPal, Wells Fargo and Yahoo! Inc.

Sites selling child pornography will be identified and reported to a tip line; companies will block transactions relating to those sites. "I haven’t seen anything like it," Andrew Oosterbaan, chief of the U.S. Department of Justice’s child exploitation section, said at a recent news conference.

The coalition will be working with the National Center for Missing and Exploited Children’s tipline (www.cybertipline.com). The tipline, which was established through a congressional mandate, has come to be known as the "911 for the Internet."

Established in 1984, the national center is a nonprofit organization that works with the U.S. Department of Justice’s Office of Juvenile Justice and Delinquency Prevention. It has assisted the department with nearly 120,000 missing child cases; more than 102,000 of those children have been found. The tipline for child-pornography Web sites has handled more than 350,000 tips, Allen said.

"The scope of the problem is much greater than we ever thought," Allen told USA Today. "It’s mind-boggling."

On June 5, MasterCard officials announced that the company had become a sponsor of the National Center for Missing and Exploited Children and had donated $100,000 to the organization.

"The systems and processes MasterCard has specifically developed to combat the use of payment cards for illegal activities provide us with excellent tools and resources to help NCMEC eliminate what has sadly become a growing industry," said John Brady, senior business leader, fraud management at MasterCard, in a press release. "Through this corporate sponsorship and our ongoing involvement with the FCACP, we hope to have a positive impact on NCMEC’s work to eliminate the exploitation of children."

In testimony to a congressional committee this year, Allen said, "Child pornography has become a global crisis . . . Its victims are becoming younger. According to NCMEC data, 19 percent of identified offenders had images of children younger than 3 years old;

39 percent had images of children younger than 6 years old; and

83 percent had images of children younger than 12 years old."

He added that in one recent case, "investigators identified 70,000 customers paying $29.95 per month and using their credit cards to access graphic images of small children being sexually assaulted."

Shelby, the Alabama senator who heads the Senate Banking Committee and helped organize the financial coalition, summed it up well when he said: "If people were buying heroin and cocaine with their credit cards, people would be outraged. This is worse."