Four per cent of all results served up by major search engines are leading users to websites offering deceptive or unwanted downloads, McAfee warns in a new study.

The study, authored by independent researcher Ben Edelman, found that the number of malware results fell one percentage point compared with last year. 

Edelman evaluated the first 50 results from the 2,300 most popular keywords on Google, Yahoo, AOL, MSN and Ask.com. 

"Four out of five website visits start with a search engine query, and consumers are still exposed to hundreds of millions of risky searches per month, " said Tim Dowling, vice president of consumer growth initiatives at McAfee SiteAdvisor.

Sponsored search results, which are purchased by site owners and placed at the top or right border of the results page, were especially likely to contain dangerous websites.

The study found that 6.9 per cent of all sponsored results link to risky sites. This marks a 1.6 percentage point decrease from last year's 8.5 per cent, which the study credits to Google's efforts to reduce fraudulent or misleading sponsored listings.

Edelman, who is an assistant professor at Harvard Business School, said that the search engines are accepting advertising fees from websites which sometimes push questionable wares. 

"The search engines could do more," he told vnunet.com. "These advertisers rely completely on search engines, so the search engines are uniquely positioned to kill these businesses." 

This is not the first time that search engines, and Google in particular, have come under fire for enabling online criminals to target web users.

Security vendor Exploit Prevention Labs demonstrated in April how malware sites are using Google's AdWords programme to lure visitors to malware hosting websites.