This is posted in the Genshin Impact reddit.
Dear Travelers,
We have received feedback from some players that when opening Genshin Impact on PC, the game's anti-cheat program will automatically run in the background, and that the anti-cheat program will continue to run after exiting or uninstalling the game.
We have looked into this issue and would like to clarify the following:
After closing the game, the anti-cheat program only reads system information; it does not process, save, or upload information in any way whatsoever.
After closing the game, the anti-cheat program continues to run in order to prevent the use of certain external plug-ins that operate when the game is closed; this is to help protect the fairness of Genshin Impact for all players.
**MiHoYo has anti cheat system to check for hacker daily.