Good point, asking for a citation. It's an extraordinary claim and so requires something to back it up. A quick search turns up this quote from a 2013 Washington Post story "By September 2004, a new NSA technique enabled the agency to find cellphones even when they were turned off. JSOC troops called this “The Find,” and it gave them thousands of new targets, including members of a burgeoning al-Qaeda-sponsored insurgency in Iraq, according to members of the unit." Source: https://www.washingtonpost.com/world/national-security/nsa-g...