The only cheating I've ever seen is people changing things on their character sheet, extra skill points, and extra feat stuff like that. Usually it's by mistake. I've added wrong before and had too many skill points, but rarely have I seen anybody intentionally cheat. I think is your party is doing that then it's time to level them up because they aren't having fun at their current power level.
I haven't seen blatant cheating just people forgetting to write in something or adding in too much of something.