>>508126937It used to be easier to discriminate in the UK so you could easily find the explosive jihadi or frenchman trying to spy on you. now everyone is a welshman and it's illegal to discriminate anon.
in the USSR they had internal passport controls, iron wall, lots of corruption and everybody was ratting on each other, the bureaucracy killed itself by tracking too many targets in the end, but was still somewhat effective against spies and at spying.
I'd say our method of preventing spies is non-existent at this point.