We’d highly welcome contributions to Mattermost open source documentation based on the below information. If you’re interested in helping, please reply to this post?
Q: Am I able to limit the access of documents and files to only users on my private network?
Yes. Typically to meet this requirement an enterprise will restrict access to the Mattermost web and desktop experiences to only users on a private network, where file sharing is enabled.
It is not uncommon for mobile apps to be used in the same deployment accessible outside the private network, with MFA enabled, and then the ability to download files from Mattermost can be disabled in the System Console in Mattermost Enterprise Edition version 4.0 and later.