And thanks to a fiendish device called a SIM box, the spammers can plug dozens, even hundreds, of SIM cards—each representing a different mobile phone number—into a single phone.
By the time you’ve received a text and reported the number, there's a good chance it has been used hundreds of times and discarded.
To really put a dent in text spam, the mobile phone companies need to upgrade their spam filters. A cynic might note that the wireless providers have little incentive to expend that effort, since it costs them essentially nothing to transmit the data, and they actually profit from spam messages received by people who don’t have unlimited texting plans.
Spokespeople for Verizon and AT&T insisted to me that they’re doing all they can, and noted that the volume of mobile spam remains tiny compared to email spam.
Your surest defense is to avoid replying to any mobile spam and to hold off on typing in your cellphone number on websites you don’t fully trust.