There are literally billions of photos doing the rounds on the internet. It would be impossible to add them all but if you consider Google, Pinterest, Instagram, Facebook and Snapchat then we are talking a lot! Who owns all these photos? A recent court ruling against a photographer whose camera was snatched by a monkey which took a selfie stated that seeing an animal snapped the photo, there was no legal ownership of the picture by the photographer.
A picture you post to Facebook does belong to you but that social media site has the right to publish the picture. The work needed to retain or gain copyright is long and tedious and who knows who took a copy of it while it was sitting on FB.
There are a number of ways to copyright a photo which include things like adding metadata and sending them to yourself or even paying a few dollars and registering them with the Copyright Office in the USA. In the UK there is no system available.
How do you know your photo was being used elsewhere? You go to all the trouble of attaching one of your Canon Lenses to your camera, set exposure and distance and all the things necessary to take a great shot. The result is fantastic. You want to blow this up to poster size it’s so good. You post it on Facebook or Instagram and get lots of “Ooh’s” and “Aah’s” from friends.
Then a couple of days later you see it on the cover of a national magazine! Uh!Oh!