Don't worry if you see the "We are tracking you as a possible Cheater" warning in GTA Online — you're in the clear!
We're going to go out on a limb here and assume that if you're reading this, you don't actually cheat in GTA Online. If you do; first of all, shame; second, this won't help you.
If you've been playing the immensely popular multiplayer mode of Grand Theft Auto 5 for a while, you might have encountered the message "We are tracking you as a possible Cheater" already — we're here to tell you what it actually means.

What is the possible cheater warning?
The full message reads "We are tracking you as a possible Cheater. Start behaving yourself." and will appear on your screen as a pop-up notification, similar to the bad sport warning. Very often on various forums, social media sites and Reddit, confused players will post questions about this after receiving it — despite not cheating.
Players can get understandably concerned when seeing a warning like this — punishments for cheating in GTA Online can get quite severe, with bans wiping your progress, including all GTA$ and items, and revoking access to the game for a while or even permanently. If you haven't actually done anything wrong, that could be devastating. Think of all the hours of progress lost!
GTA Online has been fighting against hackers and cheaters practically since the moment it went, well, online. With character transfers, script users even managed to wreak havoc on next-gen console lobbies as well as older platforms and PC. Rockstar Games has constantly been updating its anti-cheat, issuing ban waves, and even going after cheat distributors with legal means.