I've only encountered one hacker. Simply put, everyone in the match had infinite ammo, so it was more hilarious than frustrating thankfully. But still, I've tried to enable invincibility before out of curiosity via standard ocarina codes from geckocodes.org, but it always catches me during "Authenticating" and disconnects me. These goldeneye hackers must be using some sort of other codes that are being kept secret or something among their community seeing as it's prevalance is MUCH lower than what you would find in let's say, Mario kart Wii.