Actress Cameron Diaz has topped a McAfee computer security firm list of the most dangerous online celebrities.

Diaz was ranked just a step ahead of box office powerhouse Julia Roberts when it came to cyber crooks using their names to lure internet users to bogus websites booby-trapped with malicious software.

Movie stars and sexy models topped an annual "Most Dangerous Celebrities" list released by northern California-based McAfee, which computer chip titan Intel is buying in a deal valued at 7.68 billion US dollars.

US President Barack Obama and failed vice-presidential candidate Sarah Palin sank to the bottom of McAfee's annual list, making them less threatening topics for internet searches.

"Cybercriminals often use the names of popular celebrities to lure people to sites that are actually laden with malicious software," McAfee warned in a release.

"Anyone looking for the latest videos or pictures could end up with a malware-ridden computer instead of just trendy content."

Internet searches centered on Diaz had a 1-in-10 chance of leading to risky websites designed to trick visitors into unwittingly downloading viruses that can seize control or computers or mine them for data, according to McAfee.

Nineteen percent of the websites in results for searches on the term "Cameron Diaz screensavers" were rigged with malicious code.

Downloading pictures or videos is particularly dangerous because nasty software can be easily concealed in files.

Searches related to Roberts, who has been promoting her film "Eat, Pray, Love," resulted in tainted websites nine per cent of the time, but the risk leapt to 20 per cent when pictures or wallpaper were downloaded.

Jessica Biel, who McAfee last year crowned "Most Dangerous Celebrity", was in third place this year with her overall risk matching that of Roberts but slightly less chance of being offered booby-trapped screensavers.

Victoria's Secret lingerie models Gisele Buendchen, Adriana Lima, and Heidi Klum were among the Top Ten most dangerous celebrities this year, while tennis stars Maria Sharapova and Andy Roddick were 13th and 14th respectively.

"This year, the search results for celebrities are safer than they've been in previous years, but there are still dangers when searching online," said McAfee Labs security researcher Dave Marcus.

"Cyber-criminals follow the same hot topics as consumers, and create traps based on the latest trends."