[edits Jan. 31] A poli sci friend recently blogged about the Ukranian government’s “text that changed the world,” a mass text message thousands of anti-government demonstrators in Kiev. She asked 1) How did the government know who was in the main square of Kiev that day? (Cell phone location) and 2) How did it send the same message to everyone at once? (Mass SMS)

Demonstrators in Kiev. From CNN 

The second question is easy: phone companies routinely provide mass-SMS services to large customers. For example, I’m on the “emergency alert” texting service of UC San Diego’s campus police. It was designed for earthquakes, but it has been used for other kinds of messages “between earthquakes.” The same message goes out to every phone number on their list.

What to do to avoid tracking? Short version: Leave your phone at home. Second best is to shut it off or switch to airplane mode, but those work only if the government is not making an effort to target you.

Finding out who is located in an area used to be tricky, but there are now numerous ways to do it, especially if the government has cooperation from the phone company.  FIRST METHOD TO FIND LOCATION: All cellphone systems keep track of what towers are in reach of your cellphone, and the approximate signal strength, so that if someone calls you, the call is routed to the correct cell. This happens whenever your phone is turned on, whether you are using it or not. This information can be searched to identify every phone number that is currently within reach of Cell Tower X. Or with a tiny bit of extra effort, to find everyone within a designated geographic area. Around the edges, there will be some errors (false positives and false negatives), but the government of Ukraine  does not need great accuracy. (And there are ways to improve the accuracy; see below.)

How can demonstrators avoid being spotted this way? We came up with several methods, from best to worst:

• Leave your phone at home. Getting protesters to do this may be one of the government’s goals.
• Bring someone else’s phone. The phone in your pocket will still receive the government’s text message, but perhaps it won’t be associated with your name.
• Turn off your phone, or put it in “airplane mode” with no radio transmissions. In principle, this should shut down all location tracking methods, because data cannot get out of the phone while it is turned off.
  • The problem with this is that surreptitious software on your phone may keep it active, even though it appears to be off. The phone company can put such a software patch on your phone at any time.
  • Also, crazy as this sounds, some Apple software used to keep a record of where you were in the past, and periodically upload it to Apple. So even though the police cannot tell where you are right now, they might still be able to get some information about it later.
• Better is to turn off the phone, AND REMOVE THE BATTERY,  and seal it inside a thick “radiation cage.” Edward Snowden apparently used his refrigerator, but that’s not very practical in the middle of a demonstration! It’s also not necessarily an effective Faraday cage. A cocktail shaker is better as well as more portable; but if you are close to a cell tower, even that is probably not sufficient. 
  • Obviously, turning off your phone reduces its usefulness. It can still be used to take pictures, but not to send them until you turn it back on.
• Turn off GPS on your phone. This reduces the accuracy of location, but again it can be bypassed in many ways.

Other methods of determining  location  are more accurate than using cellphone towers. They include SECOND METHOD the  GPS in your phone, and THIRD METHOD Wi-Fi connections. Turning them “off” will reduce the accuracy with which you can be tracked, but it  works only if the phone has not been tampered with. A front-page article in today’s NY Times says that the NSA, and other spy agencies, use streams of data that are created by many smart phone applications, including the game Angry Birds. These data streams have been controversial in the past, since they  send private information to advertising companies.

In another example, a secret 20-page British report dated 2012 included the computer code needed for plucking the profiles generated when Android users play Angry Birds. The app was created by Rovio Entertainment, of Finland, and has been downloaded more than a billion times, the company has said.

Rovio drew public criticism in 2012 when researchers claimed that the app was tracking users’ locations and gathering other data and passing it to mobile ad companies….