In the subject line, I call them “rootkits”. Certainly that Riot
Vanguard system would fit the description of something that installs
itself so deeply into your OS, and grants itself so much power to
monitor what is going on, that you really have no idea about what it
might be doing, good or bad. If it reports another game’s anti-cheat mechanism as a “security violation”, then I think you have to start to worry.