[Critical]DoS attacks on officials servers about l4d2-community-update HOT 6 CLOSED

Appreciate the detail and report, and please continue if you have more to say.

Given how rampant these attacks are and the forums getting lit up with reports, there's no longer any use hiding the fact that this issue ValveSoftware/Source-1-Games#5141 is related.

We'll push for it to be fixed, but DoS are out-of-scope for HackerOne and it'd be unprecedented and highly unlikely for Valve to accept iptables etc. as a solution, and any ETA on an engine/game code fix should not be expected.

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I did some double checking on the recorded network and actually found the same IP sitting there as well - the one that was spamming new connections:

I also found a possible quick solution that I'm going to test today:
https://superuser.com/questions/769174/limit-incoming-connections-using-iptables-per-ip

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More information from Valve:

From Valve: L4D2 Server Issues

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I saw it in the moment it was posted, so Ig it will be resolved now.
I leave it here just in case that I implemented both protection - the one I found and the one that was suggested by the reddit user in the post you linked and I didn't have any DoS on the server since.

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Reported resolved or significantly mitigated as of SRCDS update:

https://steamdb.info/app/222860/patchnotes/

If ValveSoftware/Source-1-Games#5141 persists, then it's either a different attack, or Valve's infrastructure used an iptables/firewall solution that third-party servers will also need to implement themselves, as it appears this update prioritized Valve servers.

Please submit another issue or re-open if there's further problems here.

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Hello!

I have some information about DDoS attacks and what they are doing them with.

But it would be better to talk about it privately -> mr.bonesyk
(Discord)

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