That's because at least 70 percent of all cellphone text spam is designed to defraud you in some way, according to a study by Cloudmark, a company that makes anti-spam software. In contrast, only about 10 percent of spam arriving by email is sent with that intent.
Spam in text messages may try to guide you to shady websites that will install "malware" on your phone to vacuum up all the personal data stored in it. Or the messages may urge you to dial a phone number where your personal and financial information is solicited. Whatever you provide is either used to steal your identity or sold to third parties who'll send you yet more spam texts.
In 2012, cellphone spam — often called "smishing " — has tripled compared with 2011 levels, while email-delivered spam continues to drop, following an 82 percent decrease last year.
Why? For scammers, cellphone text messages are fast, cheap, easy and effective. The thieves use inexpensive, hard-to-track prepaid phones to transmit myriad text come-ons. When word spreads of the spam du jour, the scammers simply toss the phones they're using and buy new ones.
What's more, cellphone users are three times more likely than computer users to respond to spam. "Because you always have your cellphone with you, answering it becomes more of an impulse reaction," says Cloudmark security researcher Mary Landesman.