Aliens are probably on this planet undetected just simply surviving off of our resources after their home planet became uninhabitable for whatever reason. They may mean us harm simply as entertainment here and there. They probably still have predator drive they enact from time to time. They're probably just lingering and holding onto existence as best they can because in the end that is the most important purpose for life. This will probably end up being our destiny as well eventually if we can survive complete extinction, which it seems that no matter what happens at least a couple high profile people will always be able to endure. This sounds bleak to me but i often feel the most depressing answer is probably the most correct. Eventually there will be so few life forms left in the universe just trying to hold on that the depressing reality that existence was indeed just an unimaginable fluke will set in and everything will end in a sad suffocating whimper. Take care of your family and pets. Take care of what you can. Take care.