Surely by disconnecting your PC from the Internet and bashing your cable modem with a hammer you’ll be safe from the prying eyes of the National Security Agency, right? Wrong. Like a bad sci-fi movie that keeps unveiling unlikely technologies, it’s now being reported that the NSA has been using radio waves to tap into offline PCs since at least 2008.

The National Security Agency has implanted software in nearly 100,000 computers around the world that allows the United States to conduct surveillance on those machines and can also create a digital highway for launching cyberattacks. While most of the software is inserted by gaining access to computer networks, the N.S.A. has increasingly made use of a secret technology that enables it to enter and alter data in computers even if they are not connected to the Internet, according to N.S.A. documents, computer experts and American officials.