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Date: Sun, 23 Mar 2008 15:00:38 +0000
From: Rui Paulo <rpaulo@FreeBSD.org>
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Cc: freebsd-hackers@freebsd.org, freebsd-pf@freebsd.org,
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Subject: Re: FreeBSD OS Detection and Uptime
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On Sat, Mar 22, 2008 at 11:14:28PM -0300, =?ISO-8859-1?Q?Daniel_Dias_Gon=E7alves_ wrote:
> Which methods used to prevent OS detection and uptime (nmap) ?
> http://nmap.org/misc/defeat-nmap-osdetect.html#BSD
> I tried, but not work.

The TCP Drop SYN+FIN sysctl might help.

% sysctl -d net.inet.tcp.drop_synfin
net.inet.tcp.drop_synfin: Drop TCP packets with SYN+FIN set

Regards.
-- 
Rui Paulo