There's enough mechanical checks and balances on the three physical stats (Str, Dex, Con) that an attempt to play against your stats will become fairly obvious fairly quickly; though granted it's more obvious if playing a low stat as high than if underplaying a high stat which, if careful, one might get away with for some time.
With the mental stats (Int, Wis) - particularly if one largely eschews social mechanics - the only checks and balances are self-provided by the players in how they portray their PCs, and thus it's the responsibility of the players to self-provide (and self-enforce) these. Again, underplaying a high stat is very possible and can fool the table for a long time if done right. Overplaying a low stat - in other words, failing to self-regulate - can and does very quickly cross the line into bad-faith play.