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Date:      Tue, 16 Feb 1999 20:09:07 -0700
From:      Dave Richards <dave@richcon.com>
To:        freebsd-questions@freebsd.org
Subject:   "established" firewall rule
Message-ID:  <36CA32D3.FB01EAE5@richcon.com>

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Hi All,
I was recently the victim of a security breach on my FreeBSD 2.5 box
(the fault of Qualcomm's Qpopper 2.4 daemon, NOT FreeBSD).  It was not
pretty.. trojan horse programs all over... As a result, I reinstalled
with 2.8 and a firewall-enabled kernel. I think it's pretty secure now,
except for one question:

Can packets matching the "established" firewall rule be forged? I put
the following line early in my firewall to improve performance:

ipfw allow tcp from any to any established

...but I'm still a little worried that some crackerjack can forge
packets by setting the RST or ACK bits in his packets to fool the
firewall. Is this do-able??? Thanks for any insights...

-- 

Sincerely,
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 David A Richards, CNE, Network Consultant    Denver CO
 Richards Consulting   Unix/Novell/WinNT/Web+Database+CGI
 E-mail: mailto:dave@richcon.com


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