Hello!
As you might know we are doing regular (at the moment weekly) scans of exit nodes to find and help with misconfigurations or errors that have potentially serious effects for Tor network usability and performance. The results we got so far after over a year of scanning are roughly single digit numbers of exit relays per week having mostly DNS configuration issues (unbound crashed etc.)
However, this week we suddenly found almost 80 exit relays with malfunctioning DNS resolution[1] which was surprising. Additionally, after some of the servers got fixed the issue returned. DrWhax (thanks!) pointed us to a possible explanation twittered by the unredacted folks:
https://twitter.com/unredacted_org/status/1501458345219215363
It seems that someone (intentionally or not) is overwhelming unbound leading to DNS resolution issues for those exit operators that do run this local resolver, which we currently recommend.
We've opened a ticket[2] for further investigation, but I hope this email raises some awareness so that exit operators can keep and eye on the situation.
Feel free to add insights you have to the ticket. Additionally, I bet if someone would share how they do monitoring for such a problem on their exits then a lot of exit operators would be happily picking up that setup and the Tor network would win. :)
Thanks, Georg
[1] https://gitlab.torproject.org/tpo/network-health/team/-/issues/197 [2] https://gitlab.torproject.org/tpo/network-health/analysis/-/issues/30