Hilton's phone-service provider T-Mobile hasn't revealed how her data was pilfered, but the news sets a scary precedent. While most of us aren't toting around numbers for Anna Kournikova or Eminem in our address book, phones are often used to store sensitive information, says Adam Laurie, chief security officer for the London-based security firm The Bunker—including PIN numbers, alarm codes, and even safe combinations that could be lifted by a determined hacker.
Equally ominous, Finnish security firm F-Secure reported last week that the world's first mobile-phone virus, known as Cabir, had spread from the Philippines to 12 other countries. Cabir, which infects devices with Bluetooth wireless connectivity, is downloaded by unsuspecting users unaware that they're opening a virus.
Security experts advise phone owners to adopt the same precautions they should take with home computers: don't download unknown software or open suspicious messages, make certain passwords contain a mix of letters and numbers, and consider installing antivirus software. It might also be wise not to give your number to Paris Hilton.