Outdoor and device-free conversations is the practice of conducting sensitive or incriminating conversations outdoors and without electronic devices, to ensure that they are not overheard by an adversary.
Outdoor and device-free conversations are necessary because:
- Indoor spaces, including cars can contain covert surveillance devices.
- Electronic devices can be infected with malware that can turn them into covert microphones.
Outdoor conversations can be recorded with covert microphones or long-range parabolic microphones during a physical surveillance operation (with effective ranges of up to 300 meters). For example, in Italy in 2019 a microphone was hidden in a fake stone in front of a prison where gatherings were often held. For this reason, you should conduct outdoor conversations while walking, or for larger group conversations where it would be difficult to move, conduct them in spaces that change regularly and are difficult to place under audio surveillance.
During device-free conversations, you should not turn off your phone, remove its batteries, or place it in a Faraday bag, as this generates metadata about who is having sensitive conversations, when, and where. Instead, leave your phone at home. Also, a Faraday bag does not prevent audio from being captured, only from being transmitted, which could happen when the phone later reconnects to the network.
See the security culture topic.
Techniques addressed by this mitigation
| Name | Description | |
|---|---|---|
| Covert surveillance devices | ||
| Audio | To avoid being picked up by hidden microphones, sensitive conversations should not take place indoors, in cars, or at habitual outdoor locations. | |
| Mass surveillance | ||
| Video surveillance | To avoid being picked up by surveillance cameras equipped with microphones, sensitive conversations should be conducted away from surveillance cameras. | |