Re: SYN Flooding

From: Ben Okopnik (
Date: 08/13/01

Date: Sun, 12 Aug 2001 23:17:20 -0400
From: Ben Okopnik <>
Subject: Re: SYN Flooding
Message-ID: <>

On Thu, Aug 09, 2001 at 11:28:13AM -0700, Mark O'Brien wrote:
> If your Linux Kernel supports it you can turn on TCP Syncookies like this:
> # Like floodguard on a PIX
> echo -n "Enabling TCP Syncookies (floodguard)..."
> echo 1 >/proc/sys/net/ipv4/tcp_syncookies
> echo "done."
> I do this in my firewall startup scripts.

Do realize, however, that your kernel has to be compiled with
"CONFIG_SYN_COOKIES" turned on; it's off by default.

Ben Okopnik
We are just tenants on this world. We have just been given a new
lease, and a warning from the landlord. -- Arthur C. Clarke (2010)