You sure we had no double agents during the Cold War?
Of course we did. But we didn’t set ourselves up to be infiltrated by hiring members of CPUSA. That’s why Joe McCarthy irritated the left so much, because he was trying to enforce the law.
Nobody hired communists for years except those already in government and by who were communists already or perhaps strong socialists. Ike knew there were communists in government but preferred them over the fascists.