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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?)

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up vote 3 down vote accepted

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.

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"It is possible". It is happening, too. China blocks most of the public nodes. – Thilo May 24 '10 at 3:34

Need a reverse blacklist for those blocking exits as they make it hard to run an exit. Try to catch them out for bogus whois, other abuse, etc. If everyone tossed their broken routers and ran FreedomBox then there would be sufficient exits.

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what do you mean "they make it hard to run an exit" with regards to whether or not they're easily blacklisted, as the question posed? – Lizz Jan 10 '13 at 10:07

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