According to the Washington Post, Big Brother is still watching your cell phone when you turn it off.
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.
Evidently, the government has been able to monitor cell phones despite users powering them off, probably with false updates and spyware that installs a Trojan hack. This technology has been used since 2004, with a notable case in the United Arab Emirites in 2009 when thousands of Blackberry phones were found to be targeted by surveillance products designed by U.S security firm, SS8.
Remember, your phone is never truly off unless you remove the battery – a difficult task on most smartphones. The only safe way to avoid being tracked by the government and hackers is to go live in a cave.