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Intuitively, running a non-exit Tor node should bring the benefit of plausible deniability that a packet originated from your device.

Unlike exit nodes however, you would not have to worry about illegal content requested in the clear by your computer.

So it seems that running a non-exit node would have only benefits (not considering the increased traffic caused by this; assuming Tor does not have any exploitable security vulnerabilities in the relay code to compromise the relaying computer).

Does operating a non-exit relay node have any security-wise or legal issues I am not aware of?

  • Aside from the legal bit at the end it seems like a legit question – Abe Miessler Nov 30 '13 at 22:26
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    @Archimedix I didn't downvote this question, but I suggest you respect the place you're in (this site) and respect its members. They have the right to vote however they want without the need to explain themselves. Calling other members cowards for practising their rights is juvenile. Remember that you also got two anonymous upvotes. – Adi Dec 1 '13 at 0:04
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    Admitted, that was probably a bit harsh, but I think votes should be used as intended rather than at will: Does a question fit into the site, is it intelligible, too broad etc. I mean, what if I'd just go nuclear and always vote inappropriately, then create more accounts & do that again & again ? I could say voting is my right as long as I have that privilege, but that's a bad point of view. Downvoting says that a question does not belong here, and you'd wonder why; next time you dare not ask any more, so this will drive users away. Upvoting means a question fits in here & is useful. – Archimedix Dec 5 '13 at 12:11
  • Not voting at all means the question is irrelevant. I do not consider up- & downvotes to be fully complementary, and in fact, they are not, and the software knows this, therefore it costs you points to downvote, and downvotes are less valued than upvotes because the former are detrimental to user adoption of the site when used inappropriately. This is not much different to Wikipedia where countless users have given up contributing in face of edit wars etc. – Archimedix Dec 5 '13 at 12:14
  • What about the security of the computer itself ? I'm considering running a tor relay on my personal Ubuntu 14.04 computer at home (which also has my personal data on it). Could the security of my machine and my home network be compromised by using a vanilla tor relay configuration or are the steps suggested here trac.torproject.org/projects/tor/wiki/doc/OperationalSecurity needed ? – firdaus Jan 24 '15 at 18:26
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Traffic analysis can defeat your plausible deniability. When you relay traffic, there is a packet in for every packet out, but if you're an endpoint the traffic patterns look different - even though they can't see the packet contents.

I think it's very unlikely you'd get any comeback from being a non-exit relay. You may unknowingly forward illegal traffic, so there is a theoretic risk of some legal sanction depending on your local laws, but it wouldn't worry me. It's not traceable to you, and you are not able to decrypt the traffic, so there's nothing you could do to filter it.

Ultimately the risk are minor, but the benefits are minor too. I think most relays are motivated by supporting the tor project. It's a different story for exit nodes where many are motivated by wanting to sniff the exit traffic, and are willing to accept legals risks around this.

  • Traffic correlation requires the adversary to also monitor your incoming packets and becomes harder as you have a steady flow in and outbound (which is not that easy as you are using different circuits and multiple entry guard nodes), but yes, TOR is low latency which makes it a bit easier. – Archimedix Nov 30 '13 at 22:59
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    You shouldn't run any relay from your own internet connection at home as even non-exit relay IPs will be blacklisted by multiple sites like video streaming services etc. I know from my own experience. Also a non-exit relay will consume all the bandwidth you'll give it. – Jari Huttunen Jan 24 '15 at 19:07

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