A wallhack isn't a separate cheat — it's the ESP layer with occlusion turned off, so player outlines, boxes or chams keep drawing through geometry. Modern implementations use chams (recoloured player models) or glow rather than the flat boxes people picture from a decade ago.
The practical value is pre-aim and rotation: you know where someone is before the peek, so you win the duel on positioning instead of reflex. That's also why it is the highest-value module in slower, positional games.
The trade-off is behavioural. Consistently pre-firing a wall you have no audio reason to pre-fire is the most reportable thing you can do, and player reports drive far more manual reviews than most people assume.
Buyers search for this module under a few different names — Delta Force wallhack cheat, Delta Force wall hack, Delta Force see through walls, Delta Force chams, Delta Force x-ray hack — and they all describe the same thing: the wallhack module in the Delta Force editions listed below.