High-income earners are being preferentially targeted by online "phishing" scams, research has shown.
Phishing scams have become even more sophisticated
Phishing involves using e-mails with links to fake websites to trick people into revealing bank account numbers.
The study, by analysts Gartner, found that people who earn more than $100,000 received nearly 50% more phishing e-mails than lower earners.
It also found that those on higher incomes lost on average four times more money than other victims.
Overall, the number of US adults who have received a phishing e-mail has doubled from 57 million in 2004 to 109 million in 2006. Overall losses from the attacks have risen to $2.8 billion (£1.5 billion), Gartner estimates.
"The good news is that, this year, fewer people think they lost money to phishers, but when they did lose, they lost more," said Avivah Litan, vice president and distinguished analyst at Gartner.
"The average loss per victim nearly quintupled between 2005 and 2006, and the thieves seem to be targeting higher-income earners who are also more likely to transact on the internet."
The Gartner survey of 5,000 adults in the US estimated that 24.4 million Americans have been duped by a phishing e-mail in 2006.
The average loss per victim has grown four-fold to $1, 244, with about only 50% of the money ever recovered.
However, high-income adults lost an average of $4,362 the survey found.
It also showed that this group received an average of 112 phishing e-mails compared to an average of 74.
The Gartner research follows a report by the Association of Payment Clearing Services (APACS) earlier this week that also highlighted a surge in phishing scams and a rise in the amount of money lost.
In the first half of 2006 the number of recorded incidents in the UK rose 16-fold to 5,059, costing banks £23m, APACS said.
However, banks are not the only companies targeted by phishing scams. The Gartner research showed that brands such as eBay and PayPal are also impersonated in an attempt to lure victims to handover bank details.
Phishers are also becoming more sophisticated, using websites with an average life of just one hour to try to entice web users.
But companies are fighting back. The recent upgrades to the web browsers Firefox and Internet Explorer include software that flag up known phishing sites.
However, Ms Litan believes even these measures are insufficient.
"Many of the browser upgrades are still incomplete and immature in terms of protections afforded," she said.
"For at least two more years, phishing attacks will continue to increase since it's still a lucrative business for the perpetrators."