14.4.5. Server Security Mode (User-Level Security)

Server security mode was previously used when Samba was not capable of acting as a domain member server.

Note

It is highly recommended to not use this mode since there are numerous security drawbacks.
In smb.conf, the following directives enable Samba to operate in server security mode: 
[GLOBAL]
...
encrypt passwords = Yes
security = server
password server = "NetBIOS_of_Domain_Controller"
...