By Olga Kharif

Cheaters beware. In late October, Indonesian developer Sheran Gunasekera released mobile-phone software that can help someone eavesdrop on your conversations. A distrusting partner or spouse can secretly download the free application, called PhoneSnoop, onto your BlackBerry, remotely turn on the microphone, and listen to conversations held in proximity to the device.

PhoneSnoop, downloaded more than 2,000 times since its release, is one of a growing number of applications that can be downloaded onto a smartphone without a user's knowledge. FlexiSPY similarly can be downloaded onto Research In Motion's (RIMM) BlackBerry or the Apple (AAPL) iPhone. Smartphones and the growing number of people using them are becoming a bigger target for...