Sites that pay to have their links pop up on search engine result pages are nearly three times more likely to harbor or , or hassle users with spam than URLs generated by the engine’s algorithms, research released Friday claimed.

And search engines are cashing in, reported McAfee’s SiteAdvisor service. By its estimate, the search industry made $1.1 billion from risky sponsored links last year.

The study, which evaluated Google, Yahoo, MSN, AOL, and Ask.com search engines using 1,300 different keyword searches, found that about 5 percent of the links served up in the first five pages can infect computers or plague users with spam. That figure, about one link per search result page, is more than double SiteAdvisor’s Web average of 2 pecent.

Read more: Search Biz Makes $1.1 Billion Off Risky Links