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Covert listening devices

This part of the website is dedicated to small devices that are used to covertly record or intercept a conversation. Such devices are commonly known as bugs and are usually hidden inside the room where a conversation takes place, but may also be hidden inside a wall or work through it.

According to Wikipedia, a bug is a covert listening device [1]. Although many bugs have a built-in transmitter (radio bug), this is by no means mandatory. They can also be wire-based (wire bugs) or connected to existing devices (wire tap bugs). Some bugs are in fact recording devices that are collected after the conversation has taken place. Some modern bugs have a built-in video camera and a TV-transmitter, allowing the conversation to be viewed in a nearby room as well. Some devices are available from commercial shops and websites, such as The Spy Shop and eBay, whilst others are made especially for government agencies and are not available to the general public.

Bugs on this website
The Thing, also known as The Great Seal Bug, planted by the USSR in the office of the American Ambassador.
British resonant cavity microphone, similar to The Thing
Secret CIA research project to develop Passive Bugs, carried out by the NRP in The Netherlands
Hybrid mains-powered CIA surveillance transmitter ST-2A (bug)
Transistorized Russian bug used by the KGB around 1964
Easy Chair resonant cavity microphone
NERA VR-2B microwave receiver for passive listening device
290 MHz bug with TP audio masking
350 MHz bug with RP audio masking
Rectangular version of SRT-56
1500 MHz bug with RP audio masking
Low-power version of the SRT-91
Miniature 350 MHz transmitter (bug) with Dirty Pulse (DP) audio masking
Subcarrier modulated bug from another contractor
Minature 290 MHz transmitter (bug) with SC audio masking
Minature 70 MHz switch-receiver
Subminiature transmitter developed as part of the Super Pulse project
Soviet bug inside IBM Selectric typewriter - Operation GUNMAN
Using a regular telephone set as a bug - even when the handset is 'on-hook'
Simple commercial and self-build FM radio bugs
TMS TM-104 wireless contact microphone
TMS TM-105 sugar cube bug
Telephone element bug
TMS TM-109 ballpoint transmitter
Subminiture transmitter that can be hidden in the knot of a necktie
A.T.E.T. S-35 subminiature covert listening transmitter (radio bug)
Audiotel SCX subcarrier radio bug
Professional crystal-based Mactron FM radio bug
Mactron Mark II bug with built-in microphone pre-amplifier
Mactron Beacon for tracking and tracing
Telephone line bug based on a Mactron FM transmitter
Dummy bug, formed by a silicium ciode, in the shape of a hockey puck
Audiotel MCX Power Line Bug
Professional RF bug hidden inside the enclosure of a power adapter
Audiotel wall probe microphone with extremely sensitive amplifier
Czechoslovakian radio bug
Sophisticated masked subcarrier bug found at an OPEC conference in the late 1970s
Bulgarian telephone line-carrier bug
East German wired audio bug 'Bremen 20' used by the Stasi
DDR telephone line carrier bug
Stasi wired audio bug (NF)
Long-range DDR miniature 375 MHz radio bug with microphone
Short-range DDR miniature 950 MHz radio bug with built-in microphone
Medium-range DDR miniature 950 MHz radio bug with pre-amplifer
Long-range DDR miniature 950 MHz radio bug with power amplifier
Mobile 972 MHz bug with subcarrier audio-masking (DDR & Bulgaria)
RF bug 31217-132 (Botond) concealed in piece of wood
Stopfen RF bug 31217-111 (Stasi) with microphone in wooden plug (960 MHz)
Holzwurm (woodworm) RF bug 31217-1 (Stasi) in vertical stick (960 MHz)
Room audio bug used by the Romanian Securitate
High-performance mercury batteries developed for the CIA's bugs
Crystal-controlled transmitter (bug) with Motorola pager as switch receiver
Telephone line bug (POTS)
Telemetry transmitter used as vehicle tracker
OUDAUTO audio-based RF retro reflective covert listening device (bug)
FIREWALK gigabit ethernet implant
Homemade RF transmitter hidden in a telephone microphone element
Spanish valve-based bug 'BICHO' from 1953
Crystal controlled UHF FM transmitter (bug)
Crystal controlled UHF FM bug receiver
Free-running telephone bug for 100-140 MHz
CIA bug implanted in a CryptoPhone IP-19 used by WikiLeaks
LEA-AID covert listening device disguised as Motorola pager
TX-916 Body Transmitter 1W with scrambler

 Index of bugs
 Bug finding equipment

Complete surveillance systems
CIA surveillance system SRS-35
CIA surveillance system SRS-52
CIA surveillance system SRS-56
CIA surveillance system SRS-91
CIA surveillance system SRS-153
Path loss survey system
Path loss survey system (wideband)
Path loss survey system (narrowband)
United 225 Intelligence kit (body transmitter and briefcase receiver)
Related subjects
Central Intelligence Agency (USA)
National Security Agency
Power line receiver
SRR-52 listening post receiver
SRR-56 listening post receiver
Improved modular surveillance receiver (vertical model)
Improved modular surveillance receiver (horizontal model)
Modular surveillance receiver for RP and DP masked bugs
SRR-145 down-converter
SRR-153 surveillance receiver
Rohde & Schwarz EB-100 portable surveillance receiver
Rohde & Schwarz EB-200 Monitoring Receiver 10 kHz - 3 GHz
Czechoslovakian VHF or UHF bug receiver
Special receiver for BODIL B1 carrier bug
Wire tapping (eavesdropping on landlines)
Audio masking
Professional radio bugs often feature a technique known as audio masking, or just masking, to hide the intelligence from casual eavesdroppers as well as professional sweep teams. Masking commonly involves techniques like subcarrier modulation and Pulse Position Modulation (PPM).

 More about audio masking

Help us expand this section
This section of the website is by no means finished or complete. We are still looking for additional bugs to expand our collection and show them on the website. We are particularly interested in bugs that were used by the Stasi, the secret police of the former DDR (East Germany). If you have any bugs or related devices that are not shown here, please contact us.

Four different versions. From front to rear: the original Mactron, the Beacon, the Mark II and a prototype of the Mark III

  1. Looking towards the future: the changing nature of intrusive
    surveillance and technical attacks against high-profile targets

    Thesis 2020, Imperial College London, Department of Computing.
    Jonathan Gudgeon, November 2019.
  1. Wikipedia, Covert listening device
    Retrieved April 2013.
Further information
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Crypto Museum. Created: Monday 29 April 2013. Last changed: Tuesday, 19 March 2024 - 16:29 CET.
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