International mobile subscriber identity (IMSI) devices are used to spoof cell phone towers allowing the interception of text messages and phone calls. The most well known IMSI device is the Stingray which is what police departments use for surveillance. The existence of Stingrays was denied for years and companies that produced them are under non-disclosure agreements to protect the identity of purchasers.
The use of IMSI interceptors goes well beyond local law enforcement. Governments around the world take advantage of these fake cell “towers” to conduct espionage and track people and groups. The Department of Homeland Security (DHS) revealed that their National Protections and Programs Directorate (NPPD) had detected “anomalous” IMSI interceptor activity around Washington D.C.
A March 26th, 2018 letter by DHS official Christopher Krebs to Senator Ron Wyden was in response to Senator’s Wyden’s November 2017 inquiry about the use of IMSI interceptors. “According to the FCC, the equipment authorizations for each of these devices have limited their marketing and sale to federal, state, and local public safety and law enforcement officials only, and required state and local law enforcement agencies to advance coordinate with the Federal Bureau of Investigation on the acquisition and use of the equipment,” writes Krebs.
Krebs goes on to say that the use of IMSI interceptors is illegal to use by malicious actors and that the use of IMSI devices by malicious actors threatens national security. You can read the letter in full below.
The document below contains the answers to the questions in Senator Wyden’s letter in November 2017.