In April 2021 Roskomnadzor started enforcing throttling of Twitter traffic in Russia. The throttling was implemented with detection of domains t.co, twimg.com, and twitter.com wrapped in wildcards. Target website domains are being detected mostly in Server Name Indication part of TLS handshake. The latter resulted in throttling of all domains that contained "t.co" substring, including microsoft.com etc. (An example of the Scunthorpe problem) TLS extensions that would prevent censorship using SNI, such as Encrypted SNI, were already blocked in 2020.
