Consumers paid as much $7.8 billion over two years to repair or replace computers that got infected with viruses and spyware, a Consumer Reports survey found.

That figure was down from a similar survey a year ago. Still, it suggests that people are paying large sums to cope with the flood of malicious viruses and other programs that can slow computers or render them inoperable.

"There is a very high national cost to this," said Jeff Fox, technology editor of the consumer magazine. "People think they're invincible, even when this kind of money is involved."

In a nationwide survey, the magazine found that unwanted commercial e-mail, known as spam, is the biggest computer-security  problem. But viruses are the most expensive, with people paying $5.2 billion in 2004 and 2005 to repair or replace afflicted machines, the survey found.

Infections of spyware, a type of software that can track computer users' habits or collect sensitive information about them, declined slightly in the past six months, the survey found. But such infections caused almost 1 million U.S. households to replace their computers, the survey found.

Losses from phishing scams, which are fake e-mails and Web pages that request sensitive data such as bank-account passwords, increased five-fold from the previous survey, with people telling the magazine that such scams cost them $630 million in 2004 and 2005. That's an average loss of $850 per incident.

"Phishing scams are worse than they've ever been," Fox said. "The bad guys are getting very sophisticated."

Some experts caution, however, that surveys in which people are asked about financial losses can produce overestimates.

"The numbers could possibly be inflated by the way the questions are phrased, especially in an area in which most people aren't very articulate," said Robert Lichter, who runs a statistical center at George Mason University in Fairfax, Va.