about_login
The optional login page is disabled by default to make initial setup and use as easy a possible.
You can enable this page to add a password requirement by selecting the Enable passphrase check box on the Options page under Manage Passphrase.
The login page presents a text box for entering a password before other SIP pages are accessible. 
Note:
The password provides only minimal security. It is indented to prevent unauthorized change to SIP settings.