While software like NoScript prevents this, it's probably a good idea to block this protocol directly as well, just to be safe.
In short: Set "media.peerconnection.enabled" to "false" in "about:config".
Explained:
If you want to make sure every single WebRTC related setting is really disabled change these settings:
Now you can be 100% sure WebRTC is disabled.
WebRTC cannot be fully disabled in Chrome, however it is possible to change its routing settings (and prevent leaks) using an extension. Two open source solutions include WebRTC Leak Prevent (options may need to be changed depending on the scenario), and uBlock Origin (select "Prevent WebRTC from leaking local IP addresses" in Settings).
Chrome on iOS, Internet Explorer and Safari does not implement WebRTC yet. But we recommend using Firefox on all devices.