Although you can restrict the creation of database objects in master, system procedures such as sp_addlogin and sp_droplogin, sp_password, and sp_modifylogin allow users to modify system tables in the database. Back up the master database frequently to record these changes.
Back up the master database after each command that affects disks, storage, databases, or segments. Always back up master after issuing any of the following commands or system procedures:
disk init, sp_addumpdevice, or sp_dropdevice
Disk mirroring commands
The segment system procedures sp_addsegment, sp_dropsegment, or sp_extendsegment
create procedure or drop procedure
sp_logdevice
sp_configure
create database or alter database