Re: [tor-relays] >23% Tor exit relay capacity found to be malicious - call for support for proposal to limit large scale attacks

[Scott Bennett <bennett@xxxxxxx>]

nusenu <nusenu-lists@xxxxxxxxxx> wrote:

>
> Pascal Terjan:
> > I am not convinced it would help large scale attacks.
> > Running 50 relays is not much and it each was providing 0.49% of
> > capacity that would give them 24.5%...
> > I would expect that an attacker would create more relays than that and
> > unless there is a good way to find out this is a single entity, they
> > will all be well below 0.5%
>
>
> Yes, they will try to circumvent thresholds by pretending to not be a group.
> The good thing is that this requires additional resources and time on the attacker side to hide
> the fact that they are adding many relays without triggering certain detections.
>
     Your proposed method of delaying the problem would impose a labor burden
on the tor project as well and would be slow to react to changes.  Why would
an automated solution not work?  For example, if the directory authorities
calculate the traffic percentages every hour or so or even every several hours,
then why not just remove a Guard or Exit flag from any guard or exit exceeding
the publicized percentage?  That would be a fast reaction and would not depend
upon multiple human actions.  You might also implement a "repeat offender"
policy, whereby if the authorities lifted a relay's Exit flag more than n times
within a month, a BadExit flag would be applied in addition, which then (and
only then) would require the operator to contact the tor project about it.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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