(Just FYI I don't know if I could put a source / article on this, but this information was information that Robert Hanssen allegedly leaked to the Russians [Aldrich Ames also leaked similar things and a lot of the same HUMINT sources]. I initially read this in a Robert Hanssen non-fic book a while ago)
Apparently, during the construction of the embassy in (edit: Moscow) -East Berlin-, the construction company (surely at the direction of the KGB / GRU) placed passive bugs in the concrete (they only transmit when blasted with microwaves at the right frequency and would avoid counter-intel sweeps unless active). They built the buildings almost pre-fab style, laying the concrete out then assembiling it. It's then when the bugs were placed.
The west eventually learned about this, if I recall correctly, it was from a Russian defector by the codename of Mother.
It was called Operation Top Hat (that's where i'd start googiling). The US knew the embassy in (edit: Moscow) -East Berlin- was bugged on the first 3 floors by the Russians as well as having secret hollow support columns with clandestine access to the building. The decision was made to just not use the first 3 floors of the embassy for classified discussion. The remaining floors were built by Americans and undoubtedly under FBI/OGA watch.
IIRC there was also a network of tunnels leading from the embassy in West Berlin to under the wall to listening posts.
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(Just FYI I don't know if I could put a source / article on this, but this information was information that Robert Hanssen allegedly leaked to the Russians [Aldrich Ames also leaked similar things and a lot of the same HUMINT sources]. I initially read this in a Robert Hanssen non-fic book a while ago)
Apparently, during the construction of the embassy in (edit: Moscow) -East Berlin-, the construction company (surely at the direction of the KGB / GRU) placed passive bugs in the concrete (they only transmit when blasted with microwaves at the right frequency and would avoid counter-intel sweeps unless active). They built the buildings almost pre-fab style, laying the concrete out then assembiling it. It's then when the bugs were placed.
The west eventually learned about this, if I recall correctly, it was from a Russian defector by the codename of Mother.
It was called Operation Top Hat (that's where i'd start googiling). The US knew the embassy in (edit: Moscow) -East Berlin- was bugged on the first 3 floors by the Russians as well as having secret hollow support columns with clandestine access to the building. The decision was made to just not use the first 3 floors of the embassy for classified discussion. The remaining floors were built by Americans and undoubtedly under FBI/OGA watch.
IIRC there was also a network of tunnels leading from the embassy in West Berlin to under the wall to listening posts.
Edit: my memory is shot apparently. It was in Moscow, not Berlin. https://www.smithsonianmag.com/history/private-tour-cias-inc... https://www.latimes.com/archives/la-xpm-1991-07-29-mn-177-st...
I think i screwed up another thing Hanssen revealed and that was a tunnel from West Berlin to East Berlin and under the Soviet embassy.