But, if you are going to use this as a check to see if the player has a wallhack, it won't work.
A wallhack is a hook to the client's video memory, so it won't change the halflife view. If you want to create a 'wallhack check' you will have to make a clientside program, that makes a 'windows' screenshot, and send it via socket.
I know that.
Otherwise every wallhack there is would probably be detected by VAC...