Yes, you use stamps to protect your images from getting copied online and at the same time provides you with a sense of security. There are many tools/apps that can do that for you but I personally prefer doing with a free Android app called Auto Add Logo Copyright with Text on Camera Photos. You can easily add a logo, copyright stamps & trademark stickers along with text on photos captured with your built-in camera! That way you don't have to worry about adding stamps one by one to your photos. All you need is a one-time setup, that's it! Download and Start Marking your memories. I find this application extremely useful in day to day life. Hope this solves your query.
For IOS, you can use the app called Adobe Photoshop Mix. Open the app on your mobile, here the step follows: