I frequently post on a forum for several years now. A year or so ago, I started getting harassed by someone who apparently knows my daughter. He started posting some of her activities to get to me. I started a thread to tell him to stop, but he persisted. He even posted some personal information about me - my income and my health. When I told him there were laws against divulging that, he disappeared.
Now, he is back. He is now mentioning my mother by name. He does not say he is my mother, but he posted that to get on my nerves. I just told him to stop, but he continues.