[tor-relays] syn flood iptables rule

William Kane ttallink at googlemail.com
Fri Apr 2 18:36:50 UTC 2021


> Then they are modified, or ?

You don't know that, and Tor has code to defend against such attacks,
both limiting concurrent requests, creating too many circuits and
putting a threshold on connect() aka TCP SYN packets, the latter
though only being available on 0.4.6.1-alpha or later.

https://gitlab.torproject.org/tpo/core/tor/-/issues/40253

I'd advise against such firewall rules and let tor handle it.

- William

On 24/02/2021, Toralf Förster <toralf.foerster at gmx.de> wrote:
> On 2/22/21 7:29 PM, William Kane wrote:
>> A hard limit of 9 might be a little too low - then again, a legit,
>> unmodified tor binary would hold it's TCP connection established for
>> as long as needed -
> Hhm, I'm really under the impression that even 5 or 4 should be enough.
> If a client connects more often than every 15 seconds to its guard or a
> relay opens a conenction for more often than 4x per minute to another
> relay - then they are modified, or ?
>
> --
> Toralf
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