According to the Wall Street Journal, terrorists are using Skygrabber, a US$25.95 Windows application, to hack and play out video feeds in real time from Predator drones.
Thanks to the hacked feeds, which are unencrypted, the terrorists can extrapolate the US military's monitoring plans in their area.
The WSJ said that the US military discovered their video feeds were being hacked late last year when they confiscated a terrorist laptop containing multiple copies of video feeds from Predator drones.
The military's suspicions were confirmed in July this year when further hacked video feed files were found on other confiscated laptops "leading some officials to conclude that militant groups trained and funded by Iran were regularly intercepting feeds".
Incredibly, the paper claimed that the "US government has known about the flaw since the campaign in Bosnia in the 1990s", but that "the Pentagon assumed local adversaries wouldn't know how to exploit it".
The WSJ quoted Andrew Solonikov, one of the SkyGrabber developers, as saying he was unaware that his software could be used to hack drone feeds.
"It was developed to intercept music, photos, video, programmes and other content that other users download from the internet - no military data or other commercial data, only free legal content", he told the paper.