Method to Remove Aliens

I always find aliens respawning whenever I kill them and leave them alone. Unless it was only just recently before the 2 big SCs that it was changed but, every time I killed and left them alone the msg "Alien appeared" always comes out. I ll admit that ever since the 2 server checks I haven't seen much as much aliens at OB4 anymore as before (perhaps its because I don't see the usual aran hackers ccing every 2mins hitting all the mobs as he goes). The most noticable pattern is whenever that stupid transporter disappears you almost always see "Alien appeared" notice show up right after. Also, it seems that whenever I let more than 2 spawn I get even more aliens showing up, the ones that don't attack. It is really a pain to perfect since its so time consuming testing here and there. If it comes down to it and you can't seem to get rid of the last 1-2 aliens, you might as well work with what you got lol, thats what I end up doing when I'm in a rush.