Thwarting Cellular Interceptors

The United States government has been using planes equipped with cell phone interceptors to surveil large areas. Recently planes have been spotted around the Twin Cities circling areas of interest for hours and it appears that they’re equipped with surveillance equipment:

The plane’s flight path, recorded by the website, would eventually show that it circled downtown Minneapolis, the Mall of America and Southdale Center at low altitude for hours starting at 10:30 p.m., slipping off radar just after 3 a.m.

“I thought, ‘Holy crap,’ ” said Zimmerman.

Bearing the call sign N361DB, the plane is one of three Cessna 182T Skylanes registered to LCB Leasing of Bristow, Va., according to FAA records. The Virginia secretary of state has no record of an LCB Leasing. Virtually no other information could be learned about the company.

Zimmerman’s curiosity might have ended there if it weren’t for something he heard from his aviation network recently: A plane registered to NG Research — also located in Bristow — that circled Baltimore for hours after recent violent protests there was in fact an FBI plane that’s part of a widespread but little known surveillance program, according to a report by the Washington Post.


Zimmerman, who spotted the plane over Bloomington, said he pored through FAA records to find the call letters for each plane and then searched for images of them. He found photographs that show the planes outfitted with “external pods” that could house imagery equipment. He also found some of the planes modified with noise-muffling capability. That’s not common for a small plane, he said.


Other devices known as “dirtboxes,” “Stingrays” or “IMSI catchers” can capture cellphone data. Stanley said it’s still unclear what technologies have been used in the surveillance flights.

It’s unknown if these planes are surveillance craft or equipped with cell phone interceptors but the evidence of the former is great and the government’s program to use such craft for cell phone interception indicates the latter is likely. That being the case I feel it’s a good time to discuss a few tools you can use to communicate more securely with your cell phone.

Modern cellular protocols utilize cryptography. What many people don’t realize is that, at least in the case of Global System for Mobile (GSM), the cryptography being used is broken, which is why cell phone interceptors work. Furthermore cryptography is only used between cell phones and towers. This means your cellular provider, and therefore law enforcement agents, can listen to and read your calls and text messages.

What you really want is end-to-end encryption for your calls. Fortunately tools that do that already exist. Three tools I highly recommend are Signal, RedPhone, and TextSecure from Open Whisper Systems. Signal is an iOS application that encrypts both voice calls and text communications. RedPhone is an Android app for encrypting calls and TextSecure is an Android app for encrypting text communications. Signal, RedPhone, and TextSecure are all compatible with one another so iOS users can securely communication with Android users. All three applications are also easy to use. When you install the applications you register your number with Open Whisper System’s servers. Anybody using the applications will be able to see you have the applications installed and can therefore communicate with you securely. Since the encryption is end-to-end your cellular provider cannot listen to or read your calls and text messages. It also means cell phone interceptors, which rely on the weak algorithms used between cell phones and towers, will be unable to surveil your communications.

As the world becomes more hostile towards unencrypted communications we must make greater use of cryptographic tools. It’s the only defense we have against the surveillance state. Fortunately secure communication tools are becoming easier to use. Communicating securely with friends using iOS and Android devices is as simple as installing an app (granted, these apps won’t protect your communications if the devices themselves are compromised but that’s outside of the threat model of planes with cell phone interceptors).

One thought on “Thwarting Cellular Interceptors”

  1. I have to say the one thing so far that really dates Cryptonomicon as referring to the 90’s is the GSM phones being considered secure. XD

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