During the Cold War, even information that we would now think of as open source intelligence, like newspaper and magazine articles, was valid SIGINT. The closer

During the Cold War, even information that we would now think of as open source intelligence, like newspaper and magazine articles, was valid SIGINT. The closer you came to the dividing line between the blocks, the more probable it was to find this kind of information (just like you may be more likely to find maritime information in a port, as compared to the a landlocked place). This naturally attracted foreign personal and international organizations, as well, which introduced another class of targets of value. Which in turn makes overall activities more likely, which also provides a certain level of noise to hide your own activities…