These days, huge amount of images appear on the net.
One of our clients recently found that her photos posted on her blog had been used without her permission by others.
It was clear that her copyright in photos was infringed. Upon her requirements, the photos in question were removed in the end.
These kinds of troubles frequently happen and sometimes it's hard to solve.
One easy way to prevent others from using your photos without permission is to use "watermark" apps. Some watermark apps can be used for free.
Once you add the watermark on your photo, it shows that the photo belongs to you and you are copyright owner.