high number of reports + high kills to death = overwatch or vac scanning your pc
vac scans your pc
if they find hacks or steam achievement manager then they will ban you.
i believe 5-10 over watchers would review your game.
if more than 50% of them convicts you (says your hacking) then you get vac banned.
THERE IS NO SUCH THING AS OVERWATCH BAN NOW.
Overwatch bans are now officially vac bans.