https://www.nytimes.com/2021/10/25/us/politics/russia-cybersurveillance-biden.html
https://www.rosbalt.ru/world/2021/10/22/1927488.html
https://lansinginstitute.org/2021/10/12/russian-intelligence-focus-in-bulgaria/
https://carnegie.ru/commentary/85528
https://www.kp.ru/daily/28335.5/4480309/