Spam isn't just for your PC anymore. It's rapidly infecting text messaging, too, which means unsolicited ads for refinancing, discount drugs, and pornography can follow you anywhere you take your mobile phone-and even cost you money, if your carrier charges by the message.

The volume of spam text messages originating from the Internet in North America last year actually exceeded that of legitimate messages, according to Wireless Services of Bellevue, WA. Following the lead of Japan, South Korea, and the European Union, California has passed a law aimed at slowing such messages, and in December the U.S. Congress, as part of the CAN-SPAM Act of 2003, directed the Federal Communications Commission to come up with rules protecting cell-phone users nationwide from unsolicited text messages. But wireless companies and software vendors, worried that mobile spam will deter cell-phone users from subscribing to next-generation data services, aren't waiting for new regulations before enacting their own measures to stem the tide. Otherwise, the value of these services will be "completely obliterated," says Jim Manis, president of the Mobile Marketing Association, a trade group focused on the medium.