Co-authored with Patrick Mutchler. This is a project of the Stanford Security Lab. We’re studying the National Security Agency, and we need your help. The NSA has confirmed that it collects American phone records. Defenders of the program insist it has little privacy impact and is “not surveillance.” Like many computer scientists, we strongly disagree. Phone metadata is inherently revealing. We want to rigorously prove it—for the public, for Congress, and for the courts. That’s where you come in. We’re crowdsourcing the data for our study. We’ll measure how much of your Facebook information can be inferred from your phone records. Participation takes just a few minutes. You’re eligible if you’re in the United States, use an Android smartphone, and have a Facebook account. To get started, grab the MetaPhone app from Google Play.