OpenWrt can mount several filesystem that are attached to an IP Network. OpenWrt acts as a client.
OpenWrt can provide filesystems over network links; it acts as a server.
Files can be provided by other means: see filesharing
The Filesystems mentioned, support varying security. Accessible via TCP often means support for tcp-wrappers (libwrap). Blacklists/Whitelists are sometimes possible. Authentication via ldap ….