Cortrinkau's Blog

if you're going to a protest, leave your phone at home

Originally written about two weeks ago — life has gotten a little more dangerous for activists in America since then.

I'm taking a course this semester on surveillance technologies, and a few class periods ago the lesson turned to phones. "If you were going to an illegal anti-war protest in Moscow," my professor asked the class, "would you bring your cell phone?" No one raised their hand. "What about Iran?" Same response. "Hmm. Let's make it more American. What about, say, Washington, DC?"

"A fine January day, at the U.S. Capitol." January 6. The storming of the Capitol was a violent crime, of course. People died. It was an angry mob hellbent on overturning the results of an election, calling for bloodshed as they did so. We've all seen the videos, and naturally, the people who livestreamed their involvement on social media were easy to identify and arrest later. But there were also rioters who were arrested who hadn't posted about it, and who weren't in the videos. How did the FBI identify them?

In order for your phone to work, it needs to be able to connect to the nearest cell tower — the phone company needs to know which cell tower to route calls through so you can place and receive calls. (This is true for 'dumb phones' as well as any other device that has this capability.) Based on the radio frequencies your phone emits, it's easy for the phone company to do that using GPS triangulation. This happens automatically — assuming you're in an area with phone service, your phone just works.

Cell towers can usually only identify a phone to a radius of about half a mile, but the density at which cell towers are clustered varies. In rural areas, a cell tower might have a reach of 2 miles, but in a densely packed urban area, that's much smaller. Office buildings, my professor told us, will often have a single small cell tucked in a closet functioning as a cell tower for a specific floor. The Capitol building has infrastructure to support a very high density of phones, and it can identify the location of a cell phone to within a specific room.

So. January 6, 2021 took place. A violent mob stormed the Capitol, and the arrests began almost immediately after. The FBI obtained a warrant to get data from the phone company about the location of all phones which had been in the Capitol that day. (This is the digital equivalent of a "search and seizure" under the Fourth Amendment — the U.S. government must obtain a warrant in order to place a wiretap or to obtain location data from the phone company, but that's pretty straightforward for them to do.) From there, they traced the identities of the owners of each of those phones.

It's one thing to know where someone is within a radius of half a mile. "Oh, I wasn't at the scene of the crime, I was at my friend Ted's house, he lives a few doors down!" But when you're in the same room as the crime, surrounded by other people committing that very crime, and it was a mob that did the crime, it's kinda hard to make the claim that you're innocent. Those people were put in prison (… and pardoned four years later.)

You might say, "But those guys were violent criminals, and I'm a peaceful protestor! We're not at that point yet, where peacefully protesting is dangerous." No. But it seems entirely plausible for this administration to say "you know what, we don't like protesting any more."

If you're going to a protest, leave your phone at home.



Airplane mode + powering it off

My professor told us that when you put your phone in airplane mode, or even when you turn it off, it's still emitting radio frequencies that allow its location to be tracked. This is why spies in old movies will take the batteries out of their phones — so they can be sure their phones are really off. But smartphones don't really have removable batteries. Leave your phone at home.


Length of storage

Some of you might say, "We're not at that point yet," where peaceful protestors who aren't activists need to take these measures for their safety. That's fair. But location data is retained by phone companies for a certain amount of time — generally about 90 days. We're not even 90 days into this administration, it's impossible to predict where things will be by the time those 90 days have expired.


Other advice

Some of my friends raised an issue to my awareness: what do you do in case something happens? I have a couple strategies:

I have a designated "protestor fit" that I wear, for an extra layer of anonymity. Mask, sunglasses, and a hat or hood that hides my hair — a good idea if your hair is a particularly identifiable color or style. Wear sunscreen and bring a water bottle, it can be strenuous. Take care of yourself, and thanks for joining the resistance.