Iran blocked Tor, but not for long

The Tor project blog published an appeal to Tor's gateway operators to upgrade software to Tor 0.2.2.33 or Tor 0.2.3.4-alpha, so that users from Iran can again connect to the anonymizer network. The reason is that on the morning of September 13, Iran’s border routers began to recognize and filter Tor traffic.

Thanks to the help of third-party specialists, we were able to quickly understand the characteristics of the traffic filtering and release a new version of the program. Fortunately, it turned out that only minor fixes on the server side were enough for tens of thousands of Iranian users to once again get the opportunity to surf the web anonymously.

Tor tries to disguise its traffic as a normal HTTPS session as much as possible. In this case, the Iranian routers recognized it by the validity period of the SSL digital certificate. On the Tor network, certificates are changed every two hours, while regular certificate authorities issue SSL certificates for a year or more.
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Tor experts have already prepared their actions in response to the following attempts to filter traffic in Iran. They consider it more reasonable not to make changes in advance, but to wait for the opponent’s move.