Companies fighting to stop mobile phone spam

Flashing soon on a nearby phone is an "XLNT OFFR 4U." Just hit reply and call the number provided -- before realizing you've been duped.

Forty-three percent of all mobile phone text messages are now spam _ up from just 18 percent a year ago, according to Wireless Service Corp., a Washington-based company that runs text messages networks for roughly 30 cell phone carriers.

Like unsolicited junk e-mails that can clog home and work computers, mobile spammers cast out thousands of text messages in attempts to direct users to a site or to make an expensive phone call. Consumers, many of them paying a premium for the privilege of...