IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Organisation Remarks
____________________________________________________________________ .........................................
S 2.59 Procurement of a suitable modem
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: IT users, Administrator, Purchasing
The following items are to be observed for the purchase of a modem:
- Modem approval
Modems intended for connection to the public telecommunications
network in the Federal Republic of Germany require authorisation by the
Federal Post. Note: Contrary to information in many modem manuals,
commissioning of an approved modem in the Federal Republic of Germany
need no longer be reported to the telephone utility (Telekom).
- Design
An internal modem is advantageous in that its configuration can only be
changed on the computer in which it is integrated. If this computer has
access protection features, they can be used to safeguard the modem
configuration data. At the same time use of the modem can be restricted to
authorised persons. Manipulation of an internal modem is difficult due to
its integration in the computer. In networked systems devoid of such
protective mechanisms (e.g. some Peer-to-Peer networks), internal modems
are disadvantageous due to the possibility of their unregulated operation
from all workplaces.
An external modem can be locked in a safe place after usage. It also offers
the advantage of showing its current-status indication capability via various
displays and the integrated loudspeaker. By means of the loudspeaker, it
can be heard when a connection has been set up from outside or whether an
application is trying to transfer information via the installation and the
system configuration to the manufacturer without being instructed to do so.
A further advantage of an external modem is that it can be switched on
solely for the duration of the data transmission independent of the IT
system, thus ensuring that the most recent connection has been terminated
and that no connection can be established from outside. A disadvantage of
external modems is the possibility of connecting them to unprotected IT
systems for the purpose of manipulating the configuration data or reading
out stored passwords.
Due to their size, PCMCIA modems offer the advantage of easy storage
after use. Secure storage prevents them from being connected to
unprotected computers for the purpose of manipulation.
- Transmission rate
The higher the transmission rate of a modem, the shorter the transmission
time, and the lower the cost of transmitting large quantities of data with it.
First, the transmission rate required for the application should be
determined. Sufficient values are, for example, 2400 bits/sec. for ASCII
terminal emulation, 9600 bits/sec. for fax transmissions, currently 14400
bits/sec. in the case of Datex-J (T-Online). The highest possible trans-
____________________________________________________________________ .........................................
IT-Baseline Protection Manual: Oktober 2000