Don't talk: your cell phone may be eavesdropping.

Thanks to recent developments in "spy phone" software, a do-it-yourself spook can now wirelessly transfer a wiretapping program to any mobile phone. The programs are inexpensive, and the transfer requires no special skill.

The latest programs can silently turn on handset microphones even when no call is being made, allowing a spy to listen to voices in a room halfway around the world. Targets are none the wiser: neither call logs nor phone bills show records of the secretly transmitted data.

More than 200 companies sell spy-phone software online, at prices as low as $50

a surprising number of people carry a mobile that has been compromised, usually by a spouse, lover, parent or co-worker.

Although security programs are available for phones, by and large users haven't given the threat much thought. If the spying keeps spreading, that may change soon.