IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
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S 4.40 Preventing unauthorised use of computer
microphones
Initiation responsibility: IT Security Management
Implementation responsibility: IT-user
The microphone on a networked computer can be used by persons having
access to the corresponding device file (e.g. /dev/audio under UNIX). Under
Windows NT the access right to the appropriate registry codes determine who
can activate the computer microphone
(HKEY_LOCAL_MACHINE\HARDWARE\). This authorisation must therefore
be granted judiciously. Access to the device file should only be possible whilst
somebody is working on the IT system. If a microphone is to be prevented
from being used in general, it must, if possible, be turned off or separated
physically from the computer.
For microphones which are integrated into computers and can only be
activated/deactivated using software, the access rights must be restricted to
authorised users. Under UNIX this is possible, for example, by depriving all
relevant users of the right to read the /dev/audio device file; under Windows
NT by depriving users of access to the appropriate registry codes. This
prevents these users from using the microphone but still allows them to play
back audio files.
On IT systems equipped with a microphone, a check must be made as to
whether access rights and ownership are changed on opening of the device. If
this is the case, or if every user should be able to use the microphone without
the administrator having to release it individually, the administrator must
provide a command which
- can only be activated once a user has logged into the IT system
- can only be activated by this user and
- withdraws the access right from this user after log-out.
If access to the microphone is not controlled by means of a secure command,
the microphone must be disconnected physically from the computer.
Additional controls:
- Can the computer's microphone be turned off or disconnected physically
from the computer?
- Who has access to the microphone's device file or to the entries in the
registry where hardware settings may be manipulated?
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IT-Baseline Protection Manual: Oktober 2000