Protect yourself online.(CR Investigates)(Illustration)(Buyers Guide)

Shielding your computer from online hazards is no longer an option. It's a necessity. What were once annoyances--viruses and spam--have become major concerns.

To investigate these and other risks online users face, we conducted two nationally representative surveys involving thousands of consumers, studied hundreds of pieces of spam and set traps to attract yet more, and tested three types of protection software.

We found that while viruses and spam continue to proliferate, they have been joined by two emerging threats, Sneaky programs called spyware can implant themselves on your hard drive as you download otherwise benign software, then track what you do online, slow your computer, or take control of your browser. Then there's "phishing," the sending of fraudulent e-mail that solicits confidential information, such as your password, by impersonating banks of other institutions online. (For more on phishing, see CloseUp, on page 14.)

Intrusions like these have cost consumers serious sums of money and wasted much time, leading many to curtail their online activity, We found a number of ways to protect against them, including software products (see Ratings, pages 17 to 19). But we also found that many consumers aren't doing their pact.

Here are some other findings of our investigation:

* In a nationally representative survey we conducted of more than 2,000 house holds with at-home Internet access, 64 percent said they had detected a virus on their computers in the past two years. More than 12 percent had found a virus 10 or more times in that period.

* In the same survey, 36 percent reported that their Web browser's home page had automatically been changed, a common symptom of spyware.