Earth is being invaded by an alien species which is pretty similar to humans, being basically the only difference that instead of using for war destruction by weapons, they have developed technology that can mind control any biological being unless they have certain defenses against that, be it showing some images that can make them lose their will and embed some command, or sounds, or substances that can either breathed, ingested, or absorbed via skin (this isn't very realistic, but well, we can consider that) for the same effect. Indeed in weapon destruction abilities they are the same as a prehistoric human, as their enviroment made it extremely preferable that method of mind control instead of destruction.
My guess is that the best method would be to spy then with a drone or something and take all characterictics that would allow to identify them and then programming missiles or nuclear bombs or whatever that would identify their patterns, but maybe current techonology is still far from being able to do that.
Would this method be good to defend from them? And which other methods would be good as a defense against them?
PD: Per request I'm interested about killing them, that would be the defense, so the question could be redone as:
"Which would be a good way to kill an enemy which is already extremely risky for a human to be near it, even to see it (even if watching it via a camera)?"
PD: Edit due to Cadence request.
The mind control cannot be fought, although can be undone if the mind controlled human is captured and gets a brain operation, but this is still to be discovered how to be done by experimenting on mind controlled humans.
They don't need to be aware of humans, as long as they use the mind control in whatever situation method any human would be mind controlled if he is reached by the mind control method.
As I told, the can control any biological being (which has a brain) by adjusting these methods as needed, their weak point is that they are "physically weak", for example a robot with an armor and a sword could get rid of a lot of them, if would be like a caveman fighting against a medieval warrior.
Also, technologically speaking the story is set in present, whatever we have at our disposal now.