IT Baseline Protection Manual - The Information Warfare Site

Threats Catalogue Deliberate Acts Remarks
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T 5.39 Infiltrating computer systems via
communication cards
A communications card (e.g. an ISDN card or an internal modem, but also an
external modem) is capable of automatically receiving incoming calls.
Depending on the installed communications software and its configuration,
this makes it possible for callers to access the connected IT system without
being detected.
An external computer can be connected as a terminal to a server via a
communication card. If the user logs off after a terminal session but the line
stays connected, an external computer can be used for access just like the local
terminal. This allows third parties, who have access to this computer, the
opportunity to try out user IDs and passwords. It is even more dangerous if the
line is interrupted without the user at the local terminal being logged-off
automatically. The next caller could then work with the same user ID, without
any need to log on to the system Through this, he gets complete access to the
IT system without any identification or authentication.
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IT-Baseline Protection Manual: Oktober 2000