Is there a way to search for a specific transponder code on FR24? it is definitely not normal to have so many of those. Unless Russians have gone their own way here and just treat the 7xxx codes as normal, assignable codes?
As for blocking the data - I'm not sure how they get data from Russia. Any feed from ATC radar should be easy to block from the Russian side. ADS-B receivers would be easier, although Russia could block access to FR24 to prevent data from being sent.