No. The ability to travel interstellar distances that would be necessary for extra terrestrials to reach the Earth (if they exist) is beyond any potential technology we have thought of. First extra terrestrial intelligence would have to have evolved far beyond the level that humans have reached to produce the technology in the first place. Assuming that happened, and that they managed to find the Earth interesting out of all the planets and distances in the galaxy, let alone the universe, and decided to visit Earth, we would then have to believe that they either crashed or in some other way were captured by humans or that they were hiding in order to plot some kind of takeover (since they would not reveal themselves to anyone, even the government if they just wanted to do a secret study for scientific reasons).
But a civilization that advanced that wanted to take over or take something from the Earth wouldn’t sneak about and conspire with the government, they would just take what they wanted and we couldn’t do squat about it. Similarly, we are not holding members of such a civilization prisoner. Even if they somehow crashed and we were able to capture them, a civilization that could send them could come and rescue them, and again, we could not hope to stop them.