At some point in your life, you will become victim to someone stealing your work. This first happened to me many years ago in the early days of the web. A magazine used an image of mine without my permission. At the time I couldn't do much about. Yes, I could have taken them to court for compensation but I knew they were a small publisher and the whole process could have cost me up-front and I may not have got much compensation if I had won the case.
These days, it seems that theft of copyright material is endemic. So, what can you do to protect your work? Well, one of the most common problems is when you post your work on social media (Instagram, Twitter, Tumblr and Facebook etc). The method most folks recommend is to watermark your work. However, this isn't easy to do when using apps, for example, on your smartphone. Let's be honest, many photographers use their smartphones to take pictures, if only for the reason that it's the camera we carry around the most. If uploading via your computer then it's easier, but still something of a nuisance adding watermarks before you upload.
Somewhat easier is to reduce the size and quality of any images you upload to the web. After all, in most cases, they don't to be full resolution and maximum quality if being viewed on the web. There are plenty of applications for doing batch resizing of your images. You can also do it in most photo editors.
In my experience, I find resizing my images to 1280 pixels in the longest dimension and at 80% quality is sufficient. The image still looks great in a web browser but it's not the highest quality for printing. Yes, folk will still steal it on occasions, but it won't be appearing in a glossy book or advertising campaign. If you choose the option to retain the EXIF information embedded in the file, it will help if you do end up taking legal action against the thief. Yes, they can strip it out but most thieves don't even bother and I am not sure if most of them even know what EXIF means!
If you an artist who draws (rather than being a photographer) there are steps you can take when posting your material online. Redbubble (a photographic community) have a very good article here. I am a member of Redbubble and its a great community for artists of all kinds. You can view my portfolio here.