> The CIA knew about it in 1964 (probably not in detail) but the Soviets still used thee techniques to unmask three CIA spies per week in 1980.
If you're the CIA and you know the Soviets are using this technique, you don't fix the problem, you use it to your advantage by letting the Soviets unmask the identities of lesser spies while not putting your most important spies on the employee list.
Sacrifice three less-important spies per week? From 1964 to 1989? That must have been some amazingly amazing things they guarded if they were worth that sacrifice.
If you're the CIA and you know the Soviets are using this technique, you don't fix the problem, you use it to your advantage by letting the Soviets unmask the identities of lesser spies while not putting your most important spies on the employee list.