Spies can eavesdrop on a conversation from hundreds of feet away, just by watching a light bulb’s vibrations through a telescope.
The Soviets bugged US Embassy and Consulate typewriters with one of the world’s first keyloggers. It was a long bit of circuitry inside a supporting bar in the typewriter, capturing text by measuring magnetic disturbance as the print head moved. This was sent by radio bursts to the Soviets.
For decades the CIA owned and ran Crypto, a Swiss company that supplied cryptography equipment to many countries; naturally, the machines were rigged to give US spooks access to everyone’s communications.
Digital cameras were developed so spy satellites could send images back to earth more quickly. Before digital cameras in 1976, spy satellites used film. After the film was shot, the satellites loaded the footage into capsules and dropped them from orbit into the atmosphere for collection.
Philip K. Dick, the author of the science fiction novel “Do Androids Dream of Electric Sheep?”, published in 1968, said “There will come a time when it isn’t ‘They’re spying on me through my phone’ anymore. Eventually, it will be ‘My phone is spying on me’.” His novel was adapted into the 1982 film “Blade Runner”.