S 5.80 Protection against bugging of indoor conversations using mobile phones

Initiation responsibility: IT Security Officer, Head of IT

Implementation responsibility: IT Security Officer

The only way to rule out any eavesdropping on indoor conversions using mobile phones with certainty is to prohibit carrying along mobile phones in the room to be protected. If the government agency's or company's IT security strategy does not allow mobile phones to be brought along, this must be clearly indicated at all entrances. However, a simple notice is usually ineffective in the absence of corresponding controls.

Switching off the mobile phone provides insufficient protection since the mobile phone being switched on unobtrusively using the transmission route cannot be ruled out with sufficient certainty in the event of manipulations. The only way to prevent such an undesired start of the mobile phone would be to remove the rechargeable battery.

Mobile phone detectors

Mobile phone detectors are devices detecting when one or several mobile phones switch to transmission mode (when establishing a connection) in a restricted area.

Currently, passive warning devices reporting mobile phones in transmission mode are available on the market. The range of the devices can be configured in such a way that it is limited to the area to be monitored. It is recommendable to install such warning devices in the event of corresponding protection requirements and to activate these devices during sensitive or confidential conversations.

However, the passive detectors are not able to detect mobile phones in standby mode. In order to also detect (find) these mobile phones, an active transmission component is important for the detector. With the help of this transmission component, the mobile phone is prompted to switch to the transmission mode. Once the mobile phone is in transmission mode, it can be detected by the detector.

These active detectors make sense for meetings with sensitive content. With the help of these devices, all switched on mobile phones can be detected. Mobile phones switched on at a later point in time must register with the base station and may also be detected during this registration process. Moreover, the possible use of interfering transmitters is pointed out, which interfere with radio operations in such a way that no mobile phone reception is possible.

Currently, only passive mobile phone detectors can be recommended. Active detectors also make sense, but their use cannot be recommended in Germany, since they do not have any operating licence for the Federal Republic of Germany. The same holds true for transmitters which interfere with radio operations; they are not approved for the Federal Republic of Germany either.