BOSTON -- Searching the web for New England Patriots quarterback Tom Brady may unknowingly cause a security breach on your computer, according to a study by antivirus software maker McAfee.

In the company's third annual report of the most dangerous celebrity searches, McAfee looked at Web sites dedicated to Hollywood's most famous and tracked how many sites were created by cybercriminals hoping to infect computers that visited their sites.

Brady landed on the most dangerous list at No. 4, boosted by his recent marriage to supermodel Giesel Bundchen, who is No. 6 on the list. The couple has become a paparazzi favorite, raising the quarterback's off-the-field profile and adding to the number of people who search for him online.

"Consumers' obsession with celebrity news and culture is harmless in theory, but one bad download can cause a lot of damage to a computer," said Jeff Green, senior vice president of McAfee Avert Labs.

The No. 1 most dangerous celebrity search this year was for actress Jessica Biel. Fans searching for anything related to the former "7th Heaven" star have a one in five chance of landing on a Web site that tests positive for online threats, according to McAfee.

To conduct the study, McAfee used its SiteAdvisor technology to pinpoint the sites linked with celebrities that produce a risk for spyware, Trojans and viruses. The company then ranked the celebrities according to the volume of dangerous search hits they found.

"Cybercriminals target what's new and current, often keeping up with the latest trends in pop culture," said Shane Keats, a McAfee research analyst.

McAfee's study found that the most dangerous celebrity searches were usually linked to people who are consistently in the headlines. However, there are some exceptions. Despite President Barack Obama's high profile, he and first lady Michelle Obama ranked in the bottom third of this year's results, at No. 34 and 39.

Here are 2009's top 15 most dangerous celebrity searches:

1. Jessica Biel -- Major buzz about her figure and high-profile relationship with Justin Timberlake makes Jessica Biel an easy target for spammers and hackers. When “Jessica Biel screensavers” was searched, almost half of the sites were identified as containing malicious downloads with spyware, adware and potential viruses.
2. Beyoncé-- Beyonce tops the MTV Video Music Award nominee list, and McAfee’s results as the most frequent, highly-ranked celebrity. Inputting “Beyoncé ringtones” into a search engine yielded a dangerous Web site linking to a distributor of adware and spyware.
3. Jennifer Aniston-- A favorite among Hollywood’s leading ladies, Jennifer Aniston should be searched with caution. More than 40 percent of Google search results for “Jennifer Aniston screensavers” contained nasty viruses, including one called the “FunLove virus.”
4. Tom Brady-- The New England Patriot seems to attract many fans who want a free download of the athlete in action, but not the Trojan that comes with it.
5. Jessica Simpson-- Jessica Simpson is as dangerous to search online as she is famous. Searching for “Jessica Simpson videos” can mislead unsuspecting surfers to sites with potentially damaging downloads.
6. Gisele Bundchen-- The world’s highest-paid supermodel is a popular target for cybercriminals. A search for “Gisele Bundchen photos” can direct users to sites that breached browser security in McAfee’s tests.
7. Miley Cyrus-- Cybercriminals are using websites related to Miley Cyrus’ image to link to other harmful sites containing spyware.
8. Megan Fox, Angelina Jolie-- Both tabloid fixture Megan Fox and American icon Angelina Jolie resulted in an equal number of risky download websites, proving cybercriminals are in the business of capitalizing on the world’s most famous faces.
9. Ashley Tisdale-- The “High School Musical” star is a popular search term when it comes to searching for screensavers. A host of screensaver websites contained numerous malware-laden downloads.
10. Brad Pitt-- Appearing in the top spot last year, Brad Pitt dropped down on this year’s list, resulting in a few less, but just as dangerous websites.
11. Reese Witherspoon-- Risky websites were identified when searching for “Reese Witherspoon” and “Reese Witherspoon photos” promoting free files with hidden malware.
12. Britney Spears-- McAfee SiteAdvisor technology found a single site promoting free Britney Spears wallpaper that was embedded with more than 50 potentially infected downloads.
13. Rihanna-- Free Rihanna ringtones are some of the most sought after, but some shady vendors mislead those who subscribe by gathering and selling their personal information.
14. Lindsay Lohan-- McAfee's study flagged Lindsay Lohan screen saver sites as offering a combined 50 free screen savers infected with Trojans, viruses and spyware.
15. Kim Kardashian-- The biggest reality star in recent months is now susceptible to Internet lurkers too. A search for Kim Kardashian wallpaper and screen savers generated numerous downloads veiled with malware.