Boston-based SiteAdvisor informs people conducting Web searches whether their results include sites potentially associated with spyware, adware, spam and browser attacks. The safety ratings are displayed next to the search results with red, yellow or green icons.
The company's testing and rating service works on Google, Yahoo and Microsoft's MSN, appearing as a small button in the browser toolbar.
Although the service will be marketed to McAfee's vast consumer base, the security giant is also eyeing its use for businesses.
"This unique technology adds another dimension of strength and value to McAfee's threat database and will offer a significant corporate benefit," George Heron, McAfee chief scientist, said in a statement.
Financial terms of the deal were not disclosed.