What Should You Do if You See the Green Dot?
According to Samsung’s guidelines, you can know which app is using your camera or microphone in these quick steps.

When the notification first appears, it will have an icon showing whether the alarm is about the camera, the microphone, or both. It will then lessen to just be the dot in the upper right corner.

Pull down on the notification bar to open it and tap on the dot to expand it. This will unlock a dialogue box that tells you what’s being used (camera, microphone, or both) and what app is using them.

However, there may be an issue if you don’t remember giving the indicated app access to your camera and microphone. You need to open the settings and toggle those permissions off.