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Counter Observation Team
In the Netherlands, in the 1980s and 1990s,
the so-called Counter Observation Team — Dutch:
Contra Observatie Team — commonly abbreviated to COT, was a
highly skilled group of hobbyist
scanner-listeners, who observed the methods
and covert
operations of the Dutch police and the Dutch intelligence services,
by intercepting
their radio traffic and by using
radio direction finding.
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Contrary to regular scanner listeners – which were 'just' annoying –
the members of the COT were described by the police and the intelligence
services as damaging, as they directly interfered with – and often
frustrated – existing operations.
The existence of the COT did not go unnoticed. Intelligence service
BVD
(now: AIVD) mentioned the group in its monthly bulletin [1] of November 1990,
and called it a structural security problem. According to the BVD,
two COT members had recently appeared in a national television show,
in which they disclosed secret police locations.
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For their work, COT used a variety of high-tech equipment, consisting
of (modified) commercial-of-the-shelf products, as well has home-made devices.
It allowed them to intercept
police (radio) communication and determine the
position of members of official observation teams, using RDF.
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The image above shows two COT members in a rented car,
observing the Dutch
police during the high-profile kidnapping case of Dutch Ahold
top manager Gerrit-Jan Heijn, in 1987 and 1988.
Although the police had
encrypted its
carphone communications — using
Telsec 02 devices
— COT was still able to determine their location.
COT also made clandestine use of the
national ATF-1 carphone network,
by using commercial radio equipment, and combining it
with a home-made device that emulated the digital handshake signals,
allowing them to make free phone calls.
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The image above shows one of the clandestine homemade
ATF-1
sets used by the COT, placed on the co-seat of a regular car.
Central to the set was a square aluminium unit that imitated the telemetry
signals of a regular (legal) carphone, also known as an
ATF-1 phone phreaking unit.
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The group had also bugged some of the the vehicles of the Dutch police
and the BVD with (radio) trackers, so that their presence could be detected
during an operation. Needless to say that this capability
soon attracted the attention of criminals, who were willing to
pay good money to get access to such facilities [1].
This is one of the reasons that the group behind the COT developments,
was known by the law enforcement community as Criminal Facilities
Bureau (Dutch: Crimineel Facilitair Bureau)
and also as Service Department of the Underworld.
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In the 1980's and 90's, COT equipment turned up in several criminal
investigations and in a number of court cases. Most of the devices
were developed by hobbyists, hackers and technical students.
Most of them were initially unwitting of the fact that the equipment
was used for criminal activities and when they eventually found out,
they generally left the hackers-scene.
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COT equipment on this website
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More equipment will be added in due course.
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© Crypto Museum. Created: Tuesday 04 February 2020. Last changed: Tuesday, 05 January 2021 - 09:44 CET.
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![Freelance press photographer Henny and his partner, observing the police during the Gerrit-Jan Heijn case (1987-1988). Copyright Euro Foto [3], reproduced here by kind permission [4].](img/500846/000/full.jpg)
![Equipment for clandestine use of the Dutch ATF-1 carphone network [3].](img/500846/001/full.jpg)
