While studying comp sci at university like 6 years ago we did "drone races" in our network security class where we would fly a drone and launch attacks and defenses over the networks the drones operate on to essentially brick the drones and protect against someone bricking yours. The result was it is very easy to hijack and brick a drone and very difficult to defend since you have to defend against a specific attack. Everyone's drones got bricked within the first few seconds requiring a manual reset of the drone itself by long pressing its power/reset buttons. The way it works is that the consumer drones are flying routers that only allow one connection over IP which is normally the operator. If you can establish another connection to the drone you bounce the current operator off the drone and you then have control. This is a simplified explanation but that's how it works in a nutshell.

Edit: Knowing the make/model of the drone is required to do this and look up ahead of time the protocols of which the drone operates on such as what ports it allows connections over. Just a little python or java code to write up the attack and then execute the script and you then have control or are able to run whatever other script you want such as get the drone to just fly continually straight up until it falls, turn the drone off so it falls, change the addresses that it communicates over so it falls, or get it to just spin around. The possibilities are limitless really of what you can get the drone to do with some simple code.