At the start of the war, there were 3 million Ukrainians living in Russia, so it's not like there's a lack of Ukrainians who know the country well and consequen

At the start of the war, there were 3 million Ukrainians living in Russia, so it's not like there's a lack of Ukrainians who know the country well and consequently can probably operate successfully as spies in Russia, so I would have expected the leaders of Russian intelligence to have been deterred from this kind of action by the prospect of retaliation in kind.