From owner-freebsd-questions  Fri Dec  3  0:48:36 1999
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From: Sheldon Hearn <sheldonh@uunet.co.za>
To: "Michael Birch {PCISD Tech}" <mike@pcisd.com>
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: BSD Question 
In-reply-to: Your message of "Thu, 02 Dec 1999 15:00:52 CST."
             <000801bf3d08$5180ee20$446b01d8@pcisd.com> 
Date: Fri, 03 Dec 1999 10:48:10 +0200
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On Thu, 02 Dec 1999 15:00:52 CST, "Michael Birch {PCISD Tech}" wrote:

> Can you tell me how to shut off SMTP ping requests from being answered =
> by my machine.

Are you sure you don't mean ICMP instead of SMTP?  I've never heard of
an SMTP ping request. :-)

If you meant ICMP, there doesn't appear to be any knob that you can
fiddle with to disable ICMP replies.  You'd have to use packet
filtering, as with IPFW or IPFilter.

If you're having a specific problem with smurf attacks, where your host
responds to broadcasts, _that_ can be disabled with the following
command:

	sysctl -w net.inet.icmp.bmcastecho=0

To make this change permanent, add this line to /etc/rc.conf:

icmp_bmcastecho="NO"

Modern releases of FreeBSD default to this behaviour (not replying to
broadcast requests).

Ciao,
Sheldon.


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