Technical information

Voice Messaging Systems
6-22 Issue 7 June 2001
Security Features
Before implementing any security measures to protect the voice mail system, it is
important to understand how they work. You need to be aware of the possible
trade-offs associated with each security measure listed below.
Basic Call Transfer
With Basic Call Transfer, after a voice mail system caller enters *0, the system
performs the following steps:
1. The voice mail system verifies that the digits entered contain the same
number of digits administered for extension lengths. If call transfer is
restricted to subscribers (for the DEFINITY AUDIX System and the Avaya
I
NTUITY System only), the voice mail system also verifies that the digits
entered match the extension number of an administered subscriber.
2. If Step 1 is successful, the voice mail system performs a switch-hook flash,
putting the caller on hold.
NOTE:
If step 1 is unsuccessful, the voice mail system plays an error
message and prompts the caller for another try.
3. The voice mail system sends the digits to the switch.
4. The voice mail system completes the transfer.
With Basic Call Transfer, a caller can dial any number, provided the number of
digits matches the length of a valid extension. So, if an unauthorized caller dials a
transfer code followed by the first digits of a long-distance telephone number,
such as 91809, the voice mail system passes the numbers on to the switch. (This
is an example showing a 5-digit plan.) The switch interprets the first digit (9) as an
access code, and the following digits as the prefix digit and area code. At this
point, the caller enters the remaining digits of the phone number to complete the
call.
If call transfer is restricted to subscribers (for the DEFINITY AUDIX System and
the Avaya I
NTUITY System only), the caller cannot initiate a transfer to an
off-premises destination unless the digits entered match an administered
subscriber’s mailbox identifier; for example, 91809. To insure the integrity of the
subscriber restriction, do not administer mailboxes that start with the same digit(s)
as a valid switch Trunk Access Code. It is strongly recommended that all transfers
be restricted to subscribers when Basic Call Transfer is used.