Creepypasta headcanon
The operator's symbol looks like a harmless tattoo, but it's actually slenderman's cells set in the first layer of ur skin; if he catches u, he has a needle-like tendril that injects his black cells in the skin somewhere on ur body, those black cells will start to eat the skin cells in that area carving out the ⦻ symbol and remain there permanently (the process is painfull). And now with that symbol on u, slenderman can hear u and all noises that surround u keenly, see what u see, know where u r, control ur mind, and communicate with u through telepathy (only u can hear him so responding to him would make u look crazy in public) . The only way to remove it is by removing the part of skin it's on.
Bonus! :
If he's done with using u as his proxy the black cells will poison u on command and kill u on the spot.