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 Topic: SYN_RECV connections |
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kevinstr
Joined: 06 Jan 2017
Posts: 2
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 Posted: Sat 07 Jan '17 8:47 Post subject: SYN_RECV connections |
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Hi all,
I've noticed that my server has a lot of syn_recv connections no matter what I do. I've changed the configuration to mitigate that with syn_cookies etc but no luck.
Could that in any way be related to mpm prefork's settings? That's the only thing that I haven't touched.
Thanks in advance |
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Jan-E
Joined: 09 Mar 2012
Posts: 1248
Location: Amsterdam, NL, EU
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| Posted: Sat 07 Jan '17 13:54 Post subject: |
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| Which OS? On my Redhat/Centos6 servers I have a few firewall rules to limit SYN connections. |
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kevinstr
Joined: 06 Jan 2017
Posts: 2
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| Posted: Sat 07 Jan '17 14:03 Post subject: |
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| Jan-E wrote: | | Which OS? On my Redhat/Centos6 servers I have a few firewall rules to limit SYN connections. |
thanks for your reply.
Its ubuntu 14
You mean connlimit? |
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Jan-E
Joined: 09 Mar 2012
Posts: 1248
Location: Amsterdam, NL, EU
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| Posted: Sat 07 Jan '17 14:11 Post subject: |
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connlimit or just a limit 5/minute.
Read this post and the comments:
http://blog.bodhizazen.net/linux/prevent-dos-with-iptables/
Do a search for '-syn' on that page.
My rules:
| Code: | /sbin/iptables -A INPUT -p tcp --syn -m limit --limit 5/minute -j LOG \
--log-prefix "Firewalled packet:"
/sbin/iptables -A FORWARD -p tcp --syn -m limit --limit 5/minute -j LOG \
--log-prefix "Firewalled packet:"
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