Computer security firm Websense on Friday was warning that hackers have infected a huge number of websites with malicious code crafted to dupe Internet users.

Hundreds of thousands of legitimate websites have been booby trapped to redirect visitors to "lizamoon" addresses where they are greeted with bogus warnings that their computers have been compromised, according to Websense.

The ruse is designed to frighten people into downloading and installing fake anti-virus software, referred to as "scare-ware," portrayed as a Windows Security Center.

People who fall for the ploy, perhaps even paying for downloads, are actually installing malicious software that hackers can use to their advantage.