This do next to nothing though. Most of the DDoS-traffic, while initiated in these places, originates from botnets all over the western world. Smart fridges, enterprise routers, that sort of things. Many of them seem to come from small businesses.

And to be even more pessimistic, cutting off Russia's Internet would do nothing to stop these, because these botnets can be set up by viruses, which can in turn be initially spread by just dropping random infected USB sticks on the street in other countries. No need for a Russian-IP-hosted CNC coordinating the attack.