Harry Potter fans, beware: Emma Watson may pose a threat to your computer. One in eight sites that appear in a search for the actress are malicious, pushing malware or stealing personal data, according to McAfee. That makes her the "most dangerous" celeb on the Internet. Also watch out for Jessica Biel, Eva Mendes, and Selena Gomez. The celebrities on the security company's yearly watch list tend to be women; Jimmy Kimmel was the only man in the top 20. Cyber crime is soaring exponentially, say Symantec and McAfee: One in five users have seen their mobile gadgets or social networking profiles affected, Sky News reports.