What worries me most about the interception tech, such as stingrays, is that I myself can build one, or buy one off the shelf, and the communication systems are

What worries me most about the interception tech, such as stingrays, is that I myself can build one, or buy one off the shelf, and the communication systems are not robust enough to thwart it. Techs like GSM have serious flaws in them and agencies are using those holes to do whatever they want, with no oversight. But that's just the top of the iceberg. What about criminals?