The system is powered by McAfee’s SiteAdvisor technology, which provides always-on alerts about “risky” sites with security concerns such as spyware, adware and other malicious software that can infect and damage a user’s PC.

Sites that may harm a user’s computer just by visiting them will be eliminated completely from Yahoo Search results.

SearchScan also identifies sites that have shown bad email practices, flooding user in-boxes with spam emails.

The feature is available for Yahoo Search users in the US, Canada, UK, France, Italy, Germany, Australia, New Zealand and Spain.

The deal will also work the other way, with McAfee users gaining access to Yahoo Search in the next few months.

Vish Makhijani, senior vice president and general manager of Yahoo Search, said the new feature made searching the web even safer than ever before.

“No other search engine today offers this level of warning before visiting sites that can damage or infect a user’s PC and cost them valuable time and money,” he said.

“Through this partnership with McAfee, we can offer users a safer search experience and drive more users to make Yahoo Search their starting point on the Web.” 

McAfee’s SiteAdvisor software has been downloaded more than 135 million times.