Tor and blacklisting

Question

I'm studying Tor and its capability to provide anonymity and bypass censorship, especially when used by people of repressive countries.

I'm wondering about one thing. The nodes that are part of the "Onion Network" are limited and they're public. So, in an oppressive regime, couldn't be possible that someone with a blacklist just put a firewall blocking in this way TOR traffic? (and tracking down who's using it?)

Answer 1

It is possible to do such a thing, yes. (There even is an official list and a DNSBL service (although these are for detecting exit, not entry nodes).)

To get around this, Tor has "bridges", which don't appear on the public directory and also use a different, less likely to be blocked, port.