I'm replying to my own post to add comments based on list feedback. On 05/02/2015 06:21 PM, Mirimir wrote:
On 05/02/2015 03:40 AM, Douglas Lucas wrote:
On 05/01/2015 03:26 PM, Mirimir wrote:
Protesters, or at least key organizers, need to be running apps to detect and block IMSI catchers. And everyone not using them needs to put their phones in Faraday bags. So they also need to know how to make Faraday bags from aluminum foil and duct tape.
Some think that removing the battery, or even turning the phone off or putting it in "airplane mode", is enough. Maybe I'm too paranoid, but I don't trust either of those approaches. However, I do agree that taking one of those steps before putting the phone in the Faraday bag will prevent rapid battery discharge through high-power attempts to reach towers.
Good links to walkthroughs on both these would be greatly appreciated.
I don't use smartphones, and so don't know what works best. Searching on "detect IMSI catcher" yields hits for Android, but I see no apps for iOS. AIMSICD looks like a good app. Maybe someone who knows this stuff well can recommend one.
For the Faraday bag, see <http://www.instructables.com/id/RFID-Secure-Wallet/>. It's easy to test. Just put the phone in the bag, and call it. If it rings, there are leaks.
The hardest aspect is getting good electrical contact on all seams, including the access flap. The maximum dimension of any hole in the bag must be small, less than an inch. A gap at the seam that's an inch long, even if it's very narrow, will leak a lot.
The other thing to keep in mind is that aluminum foil gets brittle with bending, and will crack. So you need multiple layers, and the layers must be in electrical contact. Narrow strips of double-stick tape between layers are OK to provide structural stability. But it's a trade-off.
I was at Freddie Gray et al./May Day protest tonight (Friday; see tweets https://twitter.com/douglaslucas/with_replies). There was one point, a key intersection we were marching through halfway into the march, where cell reception inexplicably dropped for a few minutes. There was also, early on, someone in an Austin Police Department hat taking pictures/video from the balcony of a firefighter's station, suggesting that the cops were clued in, which would make sense given the organizing happening on facebook etc., which of course sounds like horrors to crypto snobs but in terms of mobilizing large populations is the only current, repeatedly practiced answer and an effective, if dangerous, one.