Does anybody know the name of this movie?

I cannot remember and it's driving me nuts. The film came out sometime
in the 2000s (I want to say between '02 and '07 but I'm not sure) and
it's about these young adults in a cabin together, and suddenly they
start dying. It turns out that there's this website that one of the
people hacks into and finds that everyone in the cabin is on this
site, and people are betting on (or maybe they're voting for) who will
be killed next. The adults get booted from the site and then the freak
out and don't trust one another and try to find out who among them is
a murderer yada yada yada.

I remember a scene where one girl dies from asphyxiation 'cuz someone
throws a plastic bag over her head.

The last scene is the killer (who turns out to be among the group of
people in the house) talking to some guy in the kitchen, and then he
gets shot in the head and dies anyway (I think he looks through a
peekhole or something, and gets shot, I don't quite remember).

Anyway, does anyone remember the name of this movie? It wasn't very
"big" but I want to watch it again and I have not been able to come up
with the name for over a YEAR. I think about it every once in a while
and then it drives me crazy until I eventually forget again. :P