I need to be a little cautious what I write in an open forum but there are numerous methods to hack or appear to hack the VM.

Typically the 'hacker' will create additional mailboxes and use these to break out of the system. I wont say how!

Also consider the fact that calls could be routed through the VM and ring an extn. This extn could be forwarded externally....

Suggestions:

1) Deploy Call Management software. In the UK look at the Tollring products available through Samsung. It wont stop the problem but you'll see it happening!

2) Most importantly stop the VM from dialling out. Not onyl block the relevent outcalling in the VM, go much further than this. Put all the physical VM ports into a different COS group in the phone system and block ANY outgoing access (Barring level H)

3) Never leave the VM admin mailbox password in default. Even consider changing it from time to time.

4) Never leave mailboxes with default passwords. Anyone can guess 0000 or 1234 or similar as passwords. Increase the min password length above 4 digits!

I think you get the gist of what's required to secure a system. This is not a definitive list!