Lock Symbol in front of all the cameras

Hi, I’m totally confused right now.

Why are there a lock symbol in front of all the cameras?

Milestone XProtect Administrator Guide - Devices (Devices node) link

As this question is not related to software development with the MIP SDK or XProtect integration in general, which is the focus of this forum, please ask again in a technical support case if the link to the documentation does not sufficiently answer the question.