My textures are stolen and replaced.

Hi. There is no way of protecting it and adding such feature can be considered a violation of ts4 license agreement. According to it, the game asset ( package, scripts, word, etc) file you make belongs to EA games and they allow users to freely modify and redistribute it. There are other programs that can rip these textures and meshes from any game without s4s involvement, so those who want to steal, will find a way.
However, you are the sole owner of the texture you created. While the person can extract it, they cannot use the texture with the intention of sharing with others. You can file a DMCA takedown and send it to the website that hosts the file.
Be aware that people will lie and try to paint you as a bad person to save their face. Had this one person steal the mesh of the feet I created from scratch and, when confronted, she lied about "accidentally" recreating ( an identical copy of) them by following my tutorial ( that i have never even made), so her followers jumped on me. Another one found a random paid model of feet online that looked nothing like mine and said that I stole them myself.
So yeah, you can contact a person privately and ask them to take it down first before inviting this kindergarten level of drama into your life