A bill proposed this week would require people to provide identification and officially register themselves when buying a prepaid phone. Representative Jackie Speier (D-CA), who introduced the bill, called the prepaid phone "loophole" an "egregious gap in our legal framework" that allows terrorists and criminals to prosper. The bill, Closing the Pre-Paid Mobile Device Security Gap Act of 2016, was only introduced on Wednesday and has yet to be approved by the House Judiciary Committee. It’s unclear whether it will gain more traction, but nonetheless, similar attempts to register prepaid buyers have proven controversial, as critics point out that regulations may penalize legitimate buyers.

Senator Chuck Schumer (D-NY) introduced a similar bill six years ago that would have required identification to purchase one. As explained in a New York Times story at the time, terrorists and criminals aren’t the only ones who purchase the temporary devices. Journalists use them, too, primarily for confidential conversations with sources who prefer to remain unassociated with news organizations. Victims of abuse and people with lower incomes also often purchase the phones.

terrorists and criminals aren’t the only ones who purchase prepaid phones

Apps like "Burner" have attempted to fill in for the devices, but they connect to users’ legitimate numbers, which have their names and addresses attached to them. Prepaid phones are one way to ensure anonymity, though they, too, can be wiretapped. Two years ago, researchers also uncovered a way to track and identify individual GSM phones based on unique characteristics in their radio signals. The technique could work on 3G and 4G phones, which could help investigators track devices without relying on SIM identification or other characteristics that can be changed or spoofed.