Hello,
on the evening of 2022-10-18, we (Artikel10) started getting alerts about our Tor servers, while our traffic declined sharply. When we investigated, we found that there were hundreds of thousands of TCP connections (per server) open to a single address, orders of magnitude more than any other address. We blocked this address via "ExitPolicy reject", then another one, and since then things seem to have improved.
I have thrown together a small Python script to detect this and generate "ExitPolicy reject" lines automatically: https://github.com/artikel10/surgeprotector
This is still experimental, so if you decide to give the script a try, please keep an eye on it.
Kind regards, Alexander
On 10/21/22 22:09, Alexander Dietrich wrote:
This is still experimental, so if you decide to give the script a try, please keep an eye on it.
IMO a "reload tor" is fully sufficient and should be preferrred over "restart", or ?
Years ago I wrote a bash script, which created for an ip to be blocked just an own file. Such a file can be easily removed and then tor reloaded to unblock that ip ;)
-- Toralf
Toralf Förster toralf.foerster@gmx.de hat am 22.10.2022 22:40 CEST geschrieben:
IMO a "reload tor" is fully sufficient and should be preferrred over "restart", or ?
A "reload" will update the ExitPolicy, but not drain existing connections very quickly, at least on our servers. Feel free to use whatever your preferred command/script is, though.
Kind regards, Alexander
On Samstag, 22. Oktober 2022 22:40:38 CEST Toralf Förster wrote:
On 10/21/22 22:09, Alexander Dietrich wrote:
This is still experimental, so if you decide to give the script a try, please keep an eye on it.
IMO a "reload tor" is fully sufficient and should be preferrred over "restart", or ?
Years ago I wrote a bash script, which created for an ip to be blocked just an own file. Such a file can be easily removed and then tor reloaded to unblock that ip ;)
Just tested because Applied Privacy and I have the problem that the exit policy rules do not work with some IPs¹.
Last night at 10pm: IP 79.137.192.228 had 500k connections. Added the IP to the exit policy and reloaded tor.
Policy in that order: ExitPolicy reject 79.137.192.228/32:* ExitPolicy reject *:22 ExitPolicy reject *:25 ExitPolicy accept *:*
12 hours later the IP still has over 100k connections. -> systemctl restart tor 1 hour later the IP has 0 connections :-)
¹https://gitlab.torproject.org/tpo/core/tor/-/issues/40676
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Toralf Förster