U.S. officials have confirmed that ISIS has begun using drones as a mechanism for destruction. Two years ago they began using commercial drones for surveillance, but it's looking like they've begun using them for more sinister purposes.
From the Washington Post, "They're now showing that these devices can be effective on the battlefield," said Steven Stalinsky, executive director of the Middle East Media Research Institute, a Washington nonprofit group that analyzed dozens of incidents for a new report on Islamist militant groups' use of drones. "With the way these groups use social media, my worry is that they're also putting the idea into people's heads that this is something you can now do."
The issue is that drones are relatively inexpensive and easily procured. One can easily go on Amazon (AMZN) and pick up a drone with same-day shipping, no questions asked. The U.S. military has acknowledged the growing threat and addressing it with early-detection systems and electronic jamming as well as seek-and-destroy missions where drones are being assembled and produced.