You would be very wrong in British intelligence at least - lot's of the WW2 generation of Soviet spies in the UK were openly communist, but their bosses simply

You would be very wrong in British intelligence at least - lot's of the WW2 generation of Soviet spies in the UK were openly communist, but their bosses simply couldn't believe that a well-bred englishman could be a Soviet communist (Or simply a communist, for those who were more subtle). Vetting only began in a roughly modern form decades after the first signs of infiltration became apparent. The thing about many of these people is that they were very complex - they were very effective servants during the war, but would've gladly handed orders of battle to the KGB or GRU after the war. The case of Anthony Blunt is particularly interesting: If you read Peter Wright's account of his interrogation, Blunt was no longer the KGB man he once was but his allegiances remained with his friends (i.e. other double agents). Although most of these men were sharp, Philby in particular knew exactly what he was doing (e.g. in betraying potentially hundreds of soon-to-be victims of the KGB bullet), however they nearly all possessed a deranged view of a grand communist society awaiting them upon defection - this is ignoring the obvious naivete of (I believe Blunt) either believing or choosing not to question his handler's word that those who he betrayed would not be shot. Of those who did defect, they all lived out their days surveilled and unhappy - Philby died an alcoholic who missed the cricket greatly, for example. George Blake actually only died recently, although it's hard to be sure given that he was wheeled out when convenient, but he apparently converted to Putinism. There is probably a parallel with political extremism in these spies - beneath the ideologue (unlike Aldrich Ames, for example, these men were not doing it for the money although it is potentially worth considering the economic environment they were i.e. a rich life did not solely mean money unlike during the 80s) there is often a more complicated individual, dining on deceit. As for little ladies, Melita Norwood comes to mind. On the opposite side, although not a lady, Vasili Mitrokhin had a fairly dull and tightly managed job - luckily he was very brave and we have a lot of information because of him.