How can you block it?
You just need to download an app called "Camera Block -Anti spy-malware" and install it. You can find it on Play Store just by typing the name. It has good rating and 100,000+ downloads that shows quite lot of people using it.
When you block the camera with this app it can block both cameras and for all the apps, that means you can just block the cameras with one tap and it can't be open with any other apps like WhatsApp, Viber, messenger or any other app until you unblock it again.
You can see it in the video below, although it is in different language but you can see how he tries to open with other apps and can't open the cameras.
This is just a tip, if you want to use the app or not that's completely up to you.