If you read the excerpt, you can surmise the rest of what is in the article:
“Senior defense and intelligence officials said Iranian-backed insurgents intercepted the video feeds by taking advantage of an unprotected communications link in some of the remotely flown planes’ systems.”
In the article itself it is stated “The potential drone vulnerability lies in an unencrypted downlink between the unmanned craft and ground control. The U.S. government has known about the flaw since the U.S. campaign in Bosnia in the 1990s, current and former officials said. But the Pentagon assumed local adversaries wouldn’t know how to exploit it, the officials said.”
Some of the drones do not have encryption on the downlink, so there is no hardware needed to unencrypt non encrypted data in the first place.