By Randall Mikkelsen

WASHINGTON (Reuters) - An international crackdown on Internet financial scams this year has yielded more than $2.1 billion in seized fake checks and 77 arrests in the Netherlands, Nigeria and Canada, U.S. and other authorities said on Wednesday.

The scammers, often West African organized crime groups, use ploys such as "spam" e-mail offering to pay recipients "processing fees" for depositing checks, which later turn out to be phony, and sending the ostensible proceeds to the scammer, authorities said.

The ruses are aided by U.S. financial practices that quickly credit a bank customer for deposits even though it can take far longer to discover a fake check and reclaim the money from the customer. The victims find themselves out the money they forward when the checks prove to be fake.

"Most Americans don't realize they are financially liable when they fall for these scams," Susan Grant, vice president of the National Consumers League, said at a news conference to publicize the arrests and promote awareness of the frauds.

The crackdown netted 16 arrests in Nigeria, 60 in the Netherlands and one in Canada, said Greg Campbell, U.S. Postal Inspection Service inspector in charge of global security.

"We shut down Internet cafes, we arrested scammers, and significantly disrupted the flow of fake checks into the United States," Campbell said.

Law enforcement in England also took part. Nigeria is a recognized hotbed for the financial frauds and the other countries have significant West African populations that include fraud operators, authorities said.

Three suspects from the Netherlands and Nigeria were extradited to New York and are awaiting trial, said U.S. Assistant Attorney General Alice Fischer. The United States is seeking to extradite five others.

NIGERIA

The United States is a major draw for the scammers. But other English-speaking countries are also targeted, in part because of the widespread use of English on the Internet and because of Nigeria's large English-speaking population, Campbell said.

Nigeria has brought to court 290 cases of suspected fraud, and the prosecutions have been successful in 115 of the cases so far, said Ibrahim Lamorde, head of that country's Economic and Financial Crimes Commission.

He said Nigeria is doing its best to stamp out the fake-check operations. It has seized counterfeiting equipment and convened meetings of anti-fraud officials from across Africa. But he acknowledged Nigeria has an image problem.

"The first country that comes to mind is Nigeria," Lamorde said.

Two-thirds of Americans said they received at least one potential scam contact per week, and 18 percent said they or a family member had fallen for one, in a survey conducted for an alliance of banks, consumer groups and the U.S. Postal Service.

Grant said complaints to her group about fake checks have risen 60 percent this year, and the average victim loses about $3,000 to $4,000.

Some U.S. banks have changed their practices, for example, by training tellers to better inform depositors about risks, Grant said. She called for regulations mandating that bank customers be given clearer information.

Offers can also come in direct mail. Fisher showed hand-written envelopes directed to her at a Justice Department address.

Inside were $850 checks with a Wal-Mart logo, with letters offering her a 10 percent cut if she would cash the checks and send the money back. "After you laugh and think how silly it is .. this shows it (the problem) is just completely rampant," she said.