If the unblinking stare of your MacBook's webcam has you concerned about a hacker using it to spy on you, then you may want to cover or disable the webcam when it's not in use.
The easiest and most foolproof way to stop someone from peering at you though the webcam, which Apple calls an iSight camera, is to simply cover it with a piece of tape.
If you'd rather not be left with sticky residue on your MacBook from the tape, you can disable the webcam using software, but -- disclaimer -- a hacker who gains control of your laptop may then be able to take control of your webcam. And may do so without turning on the little green light that alerts you to the webcam being active.
Apple, surprisingly, doesn't offer a setting to disable the iSight camera. With nothing in System Preferences to help us here, we must turn to an app called iSight Disabler, which you can find on the developer's website or on GitHub. The app hasn't been updated for MacOS Sierra, but a commenter on the developer's site posted a Dropbox link to a version of iSight Disabler that I can confirm works with Sierra.
I used the Dropbox link to download a Zip file, which contained a file called iSightConfigure.app. All I needed to do was launch this app and click the Disable iSight button and then enter my user password. I wish I could assign a different password for the iSight Disabler app because if someone has gained access to my MacBook, then they likely already know my password and can use this app to enable the iSight camera.
To check if your iSight camera is, in fact, disabled, you can launch Photo Booth or FaceTime. If you're staring at a black screen instead of your face, then the camera is disabled. When you want to FaceTime someone or use Photo Booth, launch the iSight Disabler app again and hit the Enable iSight button.