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Ministerium für Staatssicherheit (MfS)

Ministerium für Staatssicherheit, commonly abbreviated to MfS or Stasi, was the Ministry for State Security of the former DDR (East-Germany). It was one of the most effective and repressive secret intelligence and police organisations to have ever existed, with strong links to the Soviet KGB [1].

The origin of the MfS/Stasi dates back to the establishment of the Deutsche Demokratische Republik, or DDR — the German Democratic Republic, GDR — on 7 October 1947, shortly after the end of WWII, in the Soviet-occupied part of Germany. At that time, the agency was known as Hauptverwaltung zum Schutz des Volkseigentums (Main Directorate for the Protection of Public Property). On 8 February 1950 it was renamed to Ministerium für Staatssicherheit (Ministry for State Security), abbreviated: MfS or Stasi. Between 1953 and 1955, the Stasi operated under the control of the Innenministerium (Internal Affairs).

During the existence of the DDR, the Stasi had files on nearly everyone in the country, but also on a number of people and dissidents abroad. After the fall of the DDR in 1989 and the subsequent reunification of Germany in 1990, it became clear that a number of security services and people had tried to destroy Stasi files. Nevertheless, about 11 km of files have survived and are now publicly available through the BStU.

It is estimated that at the time of the collapse of the DDR (1989), the Stasi had 91,000 employees and 200,000 informants, the so-called Inoffizielle Mitarbeiter (IM). That is one per 50 citizens, probably the highest penetration by a security service ever [1]. The MfS was renamed to Amt für nationale Sicherheit (AfNS) at the end of 1989, and was dismantled during the course of 1990.

Stasi equipment on this website
Minox miniature and subminiature cameras Tochka-58 and Tochka-58M subminiature clockwork cameras used by the KGB (Russian variant of the Minox-A) Swiss-made Tessina subminature 35 mm camera, used by the Stasi, the CIA and several others Russian Photo Sniper (Foto Snaiper) with 300 mm telephoto lens used by the KGB Russian Krasnogorsk F-21 spy camera used by the KGB for a variety of applications Robot Star 50 clockwork camera E-120 Mini Corder and U-120 Transcriber RFT, UFT-421, body wearable surveillance radio
Tesla PR-35 (FAUN), slim-line body wearable radio for surveillance tasks Tesla PS-31, semi-portable radio with voice encoding Tesla ZO-31, radio base station with voice encoding Wired Sennheiser microphone disguised as a fountain pen Sennheiser miniature microphone Sennheiser MM-23 lapel microphone Sennheiser sub-miniature dynamic capsule Miniature microphone elements manufactured by Knowles
East-German normal-mode contact microphone with nail (Körperschall-Mikrofon) East German wired audio bug 'Bremen 20' used by the Stasi Stasi wired audio bug (NF) Bulgarian telephone line-carrier bug Bodile (Stasi: 33343) Short-range 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 RF bug 31217-1 in vertical stick (950 MHz) Travel kit with concealment area for passport and OTP Small OTP booklet used by the USSR and the DDR during the Cold War
R-353 / Proton Hungarian AK-20 spy radio set Sony ICF-2001D receiver that was used by some Soviet spies in the West M-105 AGAT
DUDEK StG-1 (T-352 / T-353) one-time tape cipher machine developed in Poland Soyka (USSR) Filin (USSR) Sinitsa (USSR) Cold War wire-line bug detector (USSR)
During the existence of the Stasi, its Hauptverwaltung Aufklärung (HVA) — Main Directorate for Reconnaissance — was responsible for domestic and foreign information gathering (espionage), and for conducting covert operations in foreign countries. For most of the time (1953-1986), the HVA was headed by the mysterious Markus Wolf [2].

Technical surveillance and countermeasures   TSCM
For observation of people and organisations, the Stasi had a wide range of technical facilities to their exposal, some of which were developed or adapted in-house. The various fields were described as assignments, each of which was identified by a letter, as shown in the table below:

  • A
    Telephone tapping
  • B
    Acoustic room monitoring (bugging)
  • D
    Optical room monitoring
  • L
    Radio, microwave radio link & satellite monitoring
  • R
    Telegraph (telex), ISDN and Data network monitoring
  • V
    Wired communication monitoring
  • X

B - Acoustic surveillance   covert listening devices
During the Cold War, citizens of the DDR (East Germany) were under constant surveillance of the Stasi, especially if they had political motives. After the fall of the Berlin Wall in 1989, it became clear they had 91,000 full-time employees and more than 200,000 informers. That is one per 50 citizens. Some sources even claim that the Stasi had one informer per 6.5 people [1]. At one time or another, nearly everyone had been asked to spy on their neighbours or their family members.

The Stasi was particularly interested in people who objected Communism and people with a public opinion, such as journalists and artists.

Over the years, many of them were subjected to surveillance for several weeks, months or even years. People were tailed, covertly photographed, their phones were tapped and listening devices (bugs) were sometimes planted in their homes.

The image on the right shows a sophisticated listening device – made in the late 1970s by a Bulgarian company – that was used by the Stasi.
Protective cap removed

It was one of many different devices and techniques that were used to monitor people in their homes, at their workplace or in public areas. In many cases the existing infrastructure – such as telephone lines and Cable TV wiring – was used to make eavesdropping easier and more efficient. In a bugging operation, the room or person under surveillance is commonly known as the Object, or the Target. For bugging an object, the Stasi had the following techniques at their disposal:

  1. NF
    Audio bugs (NF = Niederfrequenz)
  2. TF
    Carrier bugs (TF = Trägerfrequenz)
  3. HF
    Radio bugs (HF = Hochfrequenz)
  4. IR
    Infrared bugs
  5. PE
    Passive Elements
In addition, the Stasi had access to a wide range of other techniques for surveillance operations, such as telephone tapping, visual observation, radio interception, video surveillance, covert recording, covert photography, surreptitious entry, manipulation, compromise and infiltration.

When placing a bug, the most difficult job for the Stasi was to determine in which room the most interesting conversations were held, as it was practically impossible to bug each and every room in the house. Once the ideal location was established, they had to covertly place the bug.

Doing this in an inhabited house whilst the residents are out, is very dangerous, as there is always a chance that they return unexpected, or that they notice that something has changed. For this reason, the bugs were often brought in by drilling a hole in the wall from the neighbour's.
Accessing a house from the neighbour's living room. Photograph kindly provided by Detlev Vreisleben [3].

The image above shows how this was done. When the residents were out, a hole was drilled through the wall from the neigbour's living room, until just behind the plaster or wallpaper. A good place to drill with little change of discovery, was behind a power socket, as there was likely to be a similar socket at the other side. In most cases, a non-metallic tube, or probe, was placed in the hole, guiding the sound from the other side to the microphone in the neighbour's house.

For financial reasons, bugs were always in short supply in the DDR, which is why they had to be retrieved after a bugging operation had ended. This was particularly the case for carrier bugs (TF) and radio bugs (HF), but less so for wired bugs (NF) in prisons and (international) hotels, as these were often under continuous surveillance. The various types of bugs are further explained below.

Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3] Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]
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Photograph kindly provided by Detlev Vreisleben [3]

Wired systems
The diagram below gives an overview of the various techniques that were used by the Stasi for wired bugging operations. This category consists of two groups: carrier bugs, which use existing infrastructure, and audio bugs, for which dedicated wiring is used. For all systems, dedicated interfaces were available for transporting the signals via other (generally long-distance) media.

Overview of Stasi NF/TF B-technology. Click the image to see the original Stasi document.

At the left are the various wired bugs, identified by their project number. For each type of line there is a matching interface that can be used to retrieve the audio signal at the end of the line. From there, the signal is either fed to a local monitoring station (e.g. a listening post), or to a central Stasi control facility, commonly referred to as Centrales Kontrollsystem (CEKO) [4].

 Original Stasi diagram of NF and TF B-technology [A]

Wireless systems
The diagram below gives an overview of the complexity of a wireless Stasi bugging system, in its many configurations. At the left is the target area in which a miniature transmitter is hidden, here shown as the B-TX. It is a low-power transmitter which can be picked up at a terminal station in the vicinity (typically 50-150 metres away). In order to save power and to reduce the chance of discovery and exposure, some bugs were equipped with a so-called switch receiver, here shown as S-RX. It allows the transmitter to be remote controlled from the nearby terminal station.

Overview of Stasi HT B-technology. Click the image to see the original Stasi document.

For simple short-term operations, the terminal was used as the listening post. It had facilities for remote controlling the bug and for recording and monitoring the signal received from it. For more important or long-term operations, the terminal was commonly linked to the central command system (CEKO), either directly or via an intermediate station that acted as a relay.

The terminal was connected to the central CEKO system – or to the intermediate station – either wirelessly (via a bi-directional radio link) or via dedicated telephone lines, in which case audio (NF) or carrier (TF) technology was used. These links carried both audio and control signals. For medium-profile operations it was also possible to use the intermediate station as the endpoint.

Mobile improvements in the vicinity of the target

If the distance between the target area and the terminal was too large, the B-RX receiver could be enhanced with a pre-amplifier that was placed (with the antenna) closer to the target. In the same vein, a mobile switch transmitter (S-TX) was available in order to get closer to the switch receiver when activation the bug. In most cases it was placed in a car that drove past the target area.

 Original Stasi diagram of HF B-technology [B]

B1 - Audio bugs   NF
The first category (NF) was used in places where dedicated cabling for the bug could be installed, which could take hours or even days. Such bugs generally consist of a small micro­phone — often made by companies in the West such as Sennheiser and Knowles — and a miniature amplifier.

The bug was connected to the dedicated cable, and its signal could be monitored and recorded several hundred metres away at the end of that cable. In some cases, the monitoring point was patched to a central Stasi listening post via other infrascructure, such as a free telephone line.

When correctly installed and hidden, wired audio bugs can be extremely difficult to find. They can be embedded in a wall, with the sound port of the microphone requiring a tiny hole of no more than 1 mm. A good example of a such a bug is the Bremen 20 shown in the image on the right.
Potted 'Bremen 20' bug

The red and blue wires at the right are connected to the dedicated cable and the thicker grey wire leads to the microphone which was commonly hidden inside a plastered wall. If the sound port of the microphone was extended with a hollow pipe made of plastic or wood, the device could be embedded deeper inside the plastered wall, making it virtually 'invisible' to metal detectors.

Wired audio frequency bug (NF) Stasi wired audio bug (NF)
B2 - Carrier bugs   TF
Apart from the audio bugs discussed above, the Stasi could also use the existing infrastructure of a house, an apartment building, an office, a district or even a city. The bug was then installed as a parasitic device on an existing cable, using that cable to power the device and deliver its content.

Examples of existing infrastructure are the tele­phone line, the mains power cables, an intercom system in an apartment building, a common door-opener or a central antenna installation.

Such cables are usually available in every house and in some cases even in every room. As they are primarily used for the transport of other signals, the audio from a covertly installed bug had to be hidden, or masked, in such a way that it could not be picked up accidentally. This was done by modulating the audio onto a so-called carrier wave above the audible frequency range.
Bodil-B1 interior

Once modulated, the signal was injected into the cable and picked up at a tapping point several hundred metres away, where it was demodulated, recorded and eventually transcribed. A good example of a carrier wave bug is the Bulgarian bug Bodil, which is shown in the image above.

Bodil used the existing telephone line for the transport of its intelligence. Shown here without its protective cover, it could be installed nearly everywhere, for example inside a piece of furniture, inside a wooden wall or inside the telephone connection box. The audio could be retrieved with a special receiver which was placed elsewhere in the building or in some cases even outside the target area. For long-term surveillance it was even possible to patch the signal directly to a Stasi listening post by using an additional free dedicated telephone line. Similar technologies were available to bug a room via an intercom line or via the 220V power lines of the mains AC network.

Bulgarian telephone line-carrier bug (TF) used by the Stasi (Project number 33343)
B3 - Radio bugs   HF
In the rare event that the existing infrastructure could not be used for bugging a room, the Stasi used radio bugs, also known as High Frequency (HF) or Radio Frequency (RF) bugs. As they do not depend on existing cables, they can be installed nearly everywhere, even inside a movable object.

Radio bugs can be powered from the mains, but in many cases batteries were used, which greatly reduced their life span. Once the batteries ran out, they had to be swapped, for which access to the object was required. A risky undertaking.

For this reason, remote controlled bugs were sometimes used. When the bug was not needed, it could be turned off remotely by the operator at the listening station, saving precious battery power. This was useful, for example, during the night when people were sleeping, when no­body was at home, or when an office was closed.
Smallest radio bug operating at 950 MHz

Despite popular believe however, HF bugs were only used in a minority of bugging operations, as their range was very limited and they could easily be discovered by means of a special detector. In some cases they could even be discovered accidentally by someone using the radio to tune into a broadcast station. In other cases, the sound from the bug was hidden from an (un)intentional eavesdropper by using an audio-masking technique such as subcarrier frequency modulation.

Smallest radio bug with built-in microphone operating at 950 MHz 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) Hungarian RF bug 31217-132 (Botond) concealed in piece of wood
Project numbers
Although some devices have a codename, all technology that was used by the Stasi, was given a project number. This was also the case for equipment that was bought from security services in other countries, such as Bulgaria, although in some cases the project number is unknown.

Construction of the project number (31216-1)

The diagram above shows how the project number is constructed. The first digit tells us which department was responsible for it. In this case it is department 33, which was Außenstelle Beucha (Outstation Beucha). Before 1977, the prefix '3' was omitted, or the prefix 'AB' was used. The next two digits define the theme and the group within the theme. The next two digits define the actual project (within the group). If a device is part of a kit, the number behind the dash specifies the item number (within the kit). The last two digits are optional, and specify the version or variant.

Known project numbers
Audio sensitivity classes
Depending on the type of microphone that was used with (or inside) a bug, and the number of amplifier stages in the circuit, some devices had a better audio sensitivity than others, allowing the speaker to be further away from the microphone. For this reason, the audio sensitivity of a bug was often specified as one of the following classes (measured at 75 kHz deviation):

  1. 0.5 ± 0.3 µbar — low sensitivity
  2. 1.1 ± 0.3 µbar — medium sensitivity
  3. 1.7 ± 0.3 µbar — high sensitivity
BStU   Bundesbeauftragte fur die Stasi-Unterlagen
Officially: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik (DDR) — Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic (GDR).  Website
CEKO   Centrales Kontrollsystem
Contral Control System — Electronic system, developed by the Stasi in the mid-1960s — for processing telephone taps and wired covert liestening devices (bugs). The system was succeeded by CEKO 2.
ESG   Endstellengestell
German word for terminating unit or end-of-line device. In this context used for the final (remote) listening post or monitoring station.
HF   Hochfrequenz
German word for High Frequency (HF), also known as Radio Frequency (RF). Inthis context used to identify radio bugs.
HVA   Hauptverwaltung Aufklärung
Main Directorate for Reconnaissance, a department of the Stasi, responsible for foreign and domestic espionage and for foreign covert operations.
IM   Inoffizielle Mitarbeiter
Unofficial Employee — Stasi name for civil informants, inside and outside the DDR, often recruted by means of compromise and manipulation.
IR   Infrarot
German word for Infra-Red (IR). Light rays at the red end of the spectrum, invisible to the human eye.
MfS   Ministerium für Staatssicherheit
Ministery for State Security of the former DDR (East Germany); one of most effective and repressive intelligence and secret police agencies in the world. The agency is commonly known as Stasi, which is the abbreviation of Staats-Sicherheit, and had its headquarters in East-Berlin. The Stasi had strong ties with the Russian intelligence service KGB.  Wikipedia   Wikipedia Germany
NF   Niederfrequenz
German word for Audio Frequency (AF), also known as Low Frequency (LF). In this context used to identify audio bugs.
PE   Passive Element
Common expression for a covert listening device (bug) that does not need its own local power source. It is commonly powered by energy that is beamed at it from a nearby location.
Stasi   Ministerium für Staatssicherheit
TF   Trägerfrequenz
German word for Carrier Frequency (CF), commonly abbreviated to Carrier. In this context used to identify carrier bugs.
  1. Schematic overview of wired Stasi bugs
    Obtained May 2018 from BStU [4] via Detlev Vreisleben [3].

  2. Schematic overview of wireless Stasi bugs
    Obtained May 2018 from BStU [4] via Detlev Vreisleben [3].

  3. Das Telefon-Abhörsystem des MfS (Aufgabe A)
    Telephone tapping system of the Stasi (assignment A). German.
    Detlev Vreisleben, 5 May 2017 [3].

  4. Die akustische Raumkontrolle des MfS (Aufgabe B)
    Room bugging by the Stasi (assignment B). German.
    Detlev Vreisleben, 27 February 2018 [3].

  5. Die optische Raumkontrolles des MfS (Aufgabe D)
    Optical room monitoring by the Stasi (assignment D). German.
    Detlev Vreisleben, 20 January 2017 [3].
  1. Wikipedia, Stasi
    Retrieved March 2017.

  2. Wikipedia, Markus Wolf
    Retrieved May 2018.

  3. Detlev Vreisleben, Personal correspondence
    June 2017 — June 2018.

  4. Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
    Federal Commissioner for the Stasi-Records.
  1. Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik (DDR) — Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic (GDR) — officially abbreviated to BStU.

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