Stalking someone is a very serious type of harassment violation. Someone may follow you, contact you or leave packages for you repeatedly, provoking fear. This can also happen online, where the person may post your personal details, track your location or share upsetting photos of you. You can absolutely use a harassment cease and desist letter in these cases. Also, while each state has its own laws on criminal activity regarding stalking and cyberstalking, most of the time these actions are crimes, so you may be able to apply for a restraining order directly.