None of them were even known, much less found, until Ronald Pelton starting pointing them out to the russkies on a world map. At 09:45 AM 11/08/1998 -0500, John Young wrote:
NYT reports today on a new book, "Blind Man's Bluff," which reports on the US's success at placing surveillance devices on Soviet subsea communications cables around the world. With much technical detail about how it was done, beginning with the simple but overlooked idea of locating shoreline warning signs about undersea cables then tracking from there.
The devices, some up to 20 feet long for housing elaborate processing equipment, captured electronic emanations, thereby eluding detection measures aimed at physical taps. One was found by the Soviets but most were not and much information on the program is still classified.
AT&T and Bell labs built many of them. The US Navy will not comment on the book, citing national security restrictions.
-Renegade