Is your PC safe from viruses and spyware?

A national study of U.S. home computer users found many users have no idea their systems are infected with viruses or spyware, USA Today reported Monday.

In findings released by America Online and the National Cyber Security Alliance, 77 percent of the survey respondents believed they were safe from online threats, two-thirds lacked current anti-virus software and did not use any firewall protection. More than half said they didn't understand the difference between the two, informs Washington Times.

For the study, researchers conducted in-person interviews and technicians were sent to review the PCs of 329 Internet customers -- comprising 194 broadband users and 135 dial-up users -- in 12 states from Sept. 15 to Oct. 8. While the study did not focus on a large group of PC users, the results still reveal that most Americans are not cybersleuths.

"Extrapolating the percentages in our survey, this indicates that millions of Americans are at risk -- and are already infected -- by viruses, spyware, and adware," said Ken Watson, chairman of the NCSA, in a statement, wrote Washington Post.

According to the PC World, spyware was an even more common and under-appreciated problem than viruses, the survey showed. Spyware or adware programs were found on 80 percent of the computers analyzed, with an average of 93 spyware or adware components on the infected machines.

Spyware is a broad term that describes a category of programs, such as keylogging software, that illegally monitors a computer user's activity, often capturing and transmitting that information. Adware describes legally installed software, including Web page "cookies," that track user behavior such as Web surfing, often for the benefit of online advertisers.

About 90 percent of those whose computers were infected with spyware didn't know about the infections and didn't know what spyware programs are, the survey shows.