My attempt at explaining the ending.for those that have seen the movie
I see people complaining that we don't know who the hacker/ratter is. I think keeping us in the dark is kinda symbolic and done on purpose. Hackers are on a power trip and they love the fact that they can do sh!t without us knowing who it is. The part that bothered me was not knowing what happened to Emma, since we can't see what's going on.
Although, even that can be explained if you are a parent with a kid that you can't be with. Imagine talking to one of your kids on the phone and suddenly you hear a struggle and them screaming. You'd feel totally helpless. So, i think that part was added to *beep* with the viewers head. It shouldn't be marketed as a horror film. It's more of a psychological thriller.