IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
____________________________________________________________________ .........................................
S 4.37 Blocking fax sender numbers
Initiation responsibility: IT Security Management
Implementation responsibility: Fax Officer, fax mail centre
To prevent certain fax transmissions from blocking one's own fax machine,
e.g. overloading it with fax advertising campaigns, it is possible to place a
block on specified fax sender numbers.
Some modern fax machines (Group 4) are able to evaluate sender numbers
and thus prevent the reception of fax messages from particular numbers. This
applies also to fax servers which are connected to the ISDN network. The Call
Subscriber ID (CSID) can also be used to evaluate the numbers from which
incoming faxes are sent. Unfortunately, however, it is possible for originators
of faxes to suppress transmission of their numbers and for the transmitted call
numbers and the originator identifier to be tampered with.
Another alternative is for the telephone utility to set up a closed user group
(with charges) if the sender and recipient are connected to digital exchanges.
This alternative is offered by some modern PBX facilities (cf. Section 8.1
Telecommunications System (Private Branch Exchange)).
Additional controls:
- Is there a requirement to block certain originating fax numbers?
- Is the Fax Officer aware of the possibility of the safeguards outlined
above?
____________________________________________________________________ .........................................
IT-Baseline Protection Manual: Oktober 2000
Analysis of originating
call numbers by the fax
machine or fax server
Definition of closed user
groups.