To prevent cheating, the game developer implemented a Windows kernel driver that has full access to your system, even when you're not running the game. The developer claims this is totally safe and won't be exploited:
According to Riot Games, we just have to trust them on their blue eyes that their kernel driver is fully secure and won’t be exploited by malicious third parties, and that the company won’t use it to spy on people or otherwise violate their privacy. Riot states on Reddit that “multiple external security research teams” have reviewed the driver, but as far as I can tell, these reviews have not been published for public vetting.As OS News points out, Riot Games is owned by Chinese tech giant Tencent, which is known to share data with the Chinese government.
What we’re dealing with here is a rootkit, a method more and more anti-cheat systems are employing in the fight against cheating. The argument is that game developers need full, complete, and total access to your system in order to prevent you from cheating, and a kernel driver is how they do it.