You really can't see a wallhack. Really the only way to tell is when someone starts shooting somewhere before a person even gets there. That's not explained very well but I think you can get the idea.
With jitspoe's cheat detection it really is unnecessary to look for wall hackers. Just look for speedhackers since that is undtectable with the current cheat detection.
Note: There is a difference between wallhacking and spraying.
This thread could stay where it is or go in the Cheater Reports and Bans.