IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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S 5.80 Protection against bugging of indoor
conversations using mobile phones
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: IT Security Management
The only way to be sure that indoor conversations are not being bugged using
mobile phones is to prohibit the taking of mobile phones into the rooms to be
protected. If the IT security policy of an agency or company does not allow
mobile phones to be brought into the building, clear notices to this effect must
be placed on all the entrances. But without corresponding checks, a simple
notice will generally be ineffectual.
Switching off the mobile phone does not ensure sufficient protection since in
the case of manipulation there is no way of eliminating with certainty the
possibility of the phone being switched on over the radio link. The only way
to prevent this would be to remove the battery.
Mobile phone detectors
Mobile phone detectors are devices which detect whether one or more mobile
phones is in transmission mode (i.e. a conversation is taking place) within a
defined area.
Passive warning devices are available on the market which report any mobile
phones in transmission mode. The range of the devices can be adjusted so that
it is confined to the area to be monitored. It is recommended that if this kind
of protection is required, warning devices are installed and these are activated
when conversations about sensitive or confidential matters are taking place.
However, these passive detectors cannot detect mobile phones which are
currently in standby mode. Detection of such mobile phones is only possible if
the detector has an active transmitter component. This transmitter component
can then require the mobile phone to go into transmission mode. Once the
mobile phone is in transmission mode, it can be picked up with a detector.
These active detectors are appropriate for conversations which involve
sensitive material. They can detect all mobile phones that are switched on.
Any mobile phone switched on subsequently has to register itself with the
base station, and this action can be detected also. Another possibility is to use
noise pulse generators to interfere with radio operations in a spatially defined
area so that reception of mobile radio signals is not possible there.
At present only passive mobile phone detectors can be recommended. While
active detectors could also be helpful, their use cannot be recommended in
Germany as they are not approved for use in the Federal Republic of
Germany. The same applies to transmitters which jam radio operations, which
are also illegal in Germany.
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IT-Baseline Protection Manual: Oktober 2000
Passive detectors
Active detectors