The main reason that they want you to change the class of service for the prototype mailbox is that the default supervisors mailbox and password is out in the relalm of the hackers. By changing that to a COS that does not allow out dialing is so that the hackers who get in via the supervisors box and create a mailbox and use call transfer functions to output strings of numbers to dial out and call a international number that winds up going back to them and they get money for the calls.

Its always a good idea to change the default passwords and logins.

DJ