Police departments across the country have gone to great lengths to keep secret information about cell phone tracking and wiretapping devices known as “stingrays.” These devices, technically called cell site simulators or IMSI catchers, trick cell phones into communicating with the cops, alerting them to your physical location and enabling officers to wiretap your data and oral communications. Until recently, some police departments had been using this technology without any court or public scrutiny for nearly ten years. Only in the past couple of years have journalists, judges, and members of the public gotten a clearer window into law enforcement’s use of this powerful surveillance tool. But much remains secret at police departments across the country, including here in Boston.

Now we know more about the devices themselves, thanks to the Intercept‘s publication of training manuals made by the most popular device manufacturer, Harris Corporation. The training documents are worth taking a look at (see here and here), but if you want to cut to the chase and see what these devices and their antennae look like, I’ve saved you some time by copying the relevant images below. If you see anything that looks like this, watch out: You may be under surveillance.

Want to defeat stingray spying? Use Signal, which encrypts your phone calls and text messages so police can’t eavesdrop. Signal won’t stop the cops from tracking your physical location, but at least they won’t be able to hear what you’re saying.