WASHINGTON (Reuters) - Phishing scams have grown up from the unsophisticated swindles of the past in which fake Nigerian princes e-mailed victims, who would get a big windfall if they just provide their bank account number.

This Federal Bureau of Investigation (FBI) computer screen image shows an online forum called "Dark Market" where it educates users where to buy skimming devices to penetrate bank accounts, how to distribute malware through spam, and buy stolen credit cards among other things. REUTERS/FBI/Handout

Even as authorities try to stamp out that con and other e-mail and online scams, scammers are getting more wily and finding new loopholes to exploit.

The vast majority of e-mail is spam and an unknown percentage of that is meant to defraud. The scale of electronic fraud means that that the criminals can make huge profits even if only a small percentage of people are duped.

Phishing commonly refers to hoax e-mails purportedly from banks or other trustworthy sources that seek to trick recipients into revealing bank or credit card account numbers and passwords.

The U.S. government scored a big victory in November when the web hosting company McColo Corp. was taken offline. Estimates vary, but the Washington Post said that 75 percent of spam worldwide had been sent through that single company.

But the spam e-mails offering celebrity diets, cheap printer ink, erased credit card debt and amazing orgasms quickly found a new way to inboxes, according to Google’s security subsidiary Postini.

Now spammers use a variety of computers to send out spam e-mails to obscure their origins, meaning that a dramatic McColo-style takedown will be harder to reproduce, said Adam Swidler, product marketing manager for Google’s Postini.

And they’ve largely abandoned scams that are easy to see through -- like the Nigerian prince -- in favor of more sophisticated “location-based spam,” which directs the victim to a Web site discussing a local disaster or similar issue. If they click on the offered video, the Web site downloads a virus to the user’s computer, Google said in a blog on security.

Tim Cranton, a Microsoft cybersecurity expert, said there was no way to know how much money is stolen. “We don’t have a way to estimate numbers because there are so many victims that you’re not aware of,” he said.

WHAT IS ‘SMISHING’?

New technology means new ways to steal. One of the latest is “smishing,” which is nothing more than a phishing fraud sent via SMS text messaging.

E-con artists are getting more sophisticated in approaching potential victims. One tactic has been to write spam that purports to come from a trusted source, like Paypal.

When Paypal, which is owned by eBay, learned that spammers were using its name, they put a digital signature on their e-mails and asked providers like Yahoo and Google to block any e-mail purporting to come from them which did not have that signature.

“We know how many they throw away and it’s approximately speaking about 10 million a month,” said Michael Barrett, Paypal’s chief information security officer. “If the consumer never sees the e-mail in the first place then it’s hard for them to get victimized.”

“Phishing was not just impacting consumers, in terms of general loss, it was impacting their view of the safety of the Internet and that it was indirectly damaging our brand,” added Barrett.

Security experts say they are seeing more and more shifts from outright fraud, where the victim will hand over their money, to the use of malware, basically malicious software which, among other things, collects passwords and credit card numbers for thieves.

“Those will then be sold on the underground market,” said David Marcus, a threat research expert at McAfee computer security firm.

The person purchasing the passwords and card numbers will use that information to make purchases, get cash or create fake identities.

The Federal Bureau of Investigation, working with police in the United Kingdom, Turkey and Germany, shut down one such online forum called Dark Market in October 2008 which, at its peak, had more than 2,500 registered members, according an FBI press release issued at the time.

But experts agreed that they didn’t expect the problem to go away anytime soon, and that more people out of work could well mean more people like to fall for scams.

Marcus said many of the scams were nothing more than the digital equivalent of confidence tricks, although on a massive scale that can net some scammers more than $100,000 a month.

“These things only have to be 2 percent successful,” he said. “Those campaigns are sent out to tens of millions of people at the same time.