Closed source, as you should have deducted by now.
And yes, DC must be aware that "hackers will hack it", just like "haters will hate it" and "players will play it"
I go to UnrealSoftware.de yesterday. I was on portal. I looked what's new and i saw CS2D 0.1.1.9 I said "Ah .. They are again consulting about what will be new in 0.1.1.9." I was have time so I looked it and POOF New CS2D Was released.
The Vortigaunt is much more smart since it has melee it will attack you with it if your close on 1 tile near it...
The soldier on the other hand is a bit stupid like he is suppose to be... just do this - when you see a grunt run around him with a knife spinning circles...he wont bother to shoot just spin right round like a record baby round round round round...