Something is wrong with your installation if it's doing that. Mine uses 0.5% CPU. Uninstall and reinstall or check for updates. It checks network drives for installed games so it can show you the cheats for them, per the column on the left with Installed Games, etc.
It doesn't need to be. Current trainer still working. However, it only works on Single Player with BattleEye anti-cheat disabled. Possibly on a multi-player server without BattleEye but I'm not sure on that one.