[tor-relays] Tor Server - DDOS or High Load

webmaster webmaster at defcon-cc.dyndns.org
Wed Dec 3 17:17:34 UTC 2014


Hello Folks,

I'm running a relay tor server since several years.
Last week (24 Nov) I noticed a high load on the tor server (cpu load
100%). After some investigation i found out that tor causes the high
load. After killing the process the load decreases to a normal level,
but after restarting the tor process again the load increases again.

Arm log:

Could not open "" for writing: To many open files.

or

Failing because because we have 1017 connections already. Please raise
your ulimit -n
Tor's file descriptor usage is at 91%. If you run out Tor will be unable
to continue functioning.


At first I thought: Fuck, someone intruded into my machine.
But after some looking through Arm I found many (>100) INBOUND connections.

After one hour and some iptables tuning the cpu load decreases.

Could the high load caused by an attack on my machine or is this
just some small load peak?


Hope for some reply




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