The use of commercial UAVs, especially the quad-copter types, by criminals and terrorists has been going on since at least 2010 and is getting more media attention. Less well known is the more mundane use of commercial grade UAVs by military and police organizations (including peacekeepers and peace monitors). For example the U.S. Air Force has been using a commercial quad-copter and its high resolution video camera to more quickly and less expensively carry out maintenance inspections of large military aircraft like the C-17 transport or heavy bombers. Until some enterprising (and probably overworked) airman thought of this these inspections were carried out by maintainer personnel, often wearing a safety harness as they scrambled over parts of these aircraft that were taller than a multi-story building looking for small cracks or other signs of metal fatigue. This could take up to an hour per aircraft. With the quad-copter it takes less than ten minutes and the operator no longer needs a safety harness. The air force conducted some tests and found that the quad-copter inspection approach consistently gave the same results (as well as a video record of it) in less time that the traditional method.
The headline-grabbing illegal use of commercial UAVs began getting attention in 2014 when South Korea found two North Korean UAVs that had crashed on the South Korean side of the border. It later turned out that these UAVs were repainted Chinese SKY-09P commercial models. These are 12 kg (26 pound) delta wing aircraft with a wingspan of 1.92 meters (6.25 feet), propeller in the front and a payload of three kg (6.6 pounds). It is launched via a catapult and lands via a parachute. Endurance is 90 minutes and cruising speed is 90 kilometers an hour. When controlled from the ground it can go no farther than 40 kilometers from the controller. But when placed on automatic it can go about 60 kilometers into South Korea and return with photos. These things cost the North Koreans a few thousand dollars each.
The first documented regular use of commercial UAVs for criminal activities occurred on the American border with Mexico. Since at least 2011 Mexican drug smugglers were using these commercial UAVs to get cocaine across the border. These UAVs are small enough, slow enough and fly low enough to avoid radar. Operating on automatic pilot, they can fly over a hundred kilometers into the U.S. at night, drop several kilograms (apparently up to six pounds or so) and return to Mexico. Others, like the quad-copter types, have been known to make shorter, one-way trips. The larger commercial UAVs, that can be reused, cost under $10,000 and are good for at least a few trips.
The Israeli military has bought some locally developed Roetm L UAVs for their infantry to use in urban combat. What is unique about the Roetm L it is a lightweight (4.5 kg/10 pound) quad-copter based on commercial designs but modified so that it not only carries the usual day/night cameras but is also armed with two 450g (one pound) grenades that can be armed and released by operator command. With 30 minutes endurance and easily learned operation Rotem L can be carried (in a case) by one man, set up and ready to go in a minute or so and recovered for reuse. The controller has a range of up to 10 kilometers but in a dense urban environment the max range is more like 1,500 meters. The major advantage of Rotem L is that it is quiet and can be flown through open doors or windows.
Carrying one or no grenades allows Rotem L to stay airborne for up to 45 minutes. The grenades can be triggered while still aboard Rotem L to provide a self-destruct mechanism. If Rotem L lands with live grenades aboard the operator can double check the armed status of the grenades before recharging it for another mission. Rotem L can be used unarmed by police or carry tear gas or flash-bang grenades.
Islamic terrorists have increasingly used quad copters and fixed wining commercial UAVs but the Israelis have taken the lead in developing and exporting systems for detecting these commercial UAVs and taking them down without a lot of fuss or fireworks.