SMURF amplifier block list

Jason Lixfeld jlixfeld at
Fri Apr 24 02:45:41 UTC 1998

What's the difference?  If you do echo-reply, whoever initiated the ping
will never see a response because it is filtered by the echo-reply in the
first place.  Or am I missing something with the echo-reply?!  (it's late,
forgive my ignorance) =)

On Mon, 20 Apr 1998, Pete Ashdown wrote:

:jlixfeld at said once upon a time:
:>You could always "deny icmp any aaa.bbb.ccc.ddd www.ccc.nnn.mmm log" on
:>your cores.  Deny ICMP from critical portions of your network.  Create a
:>little script which tail -fs the log, parses it, sorts it and counts it.
:>If the script counts more then xxx hits on a certain IP or a certain
:>number of IPs on your network from the same source or a multiple sources
:>on the same network, you have your upstream.  Once you have them, you can
:>call them and ask them to do the same until you find the real source.
:You might want to stick in an "echo-reply" before the log.  This will
:specifically block the smurf, but won't affect any of the other ICMP which
:does have a useful purpose.  This of course will stop any of the blocked
:addresses from doing outside pings or traceroutes as well.


Jason A. Lixfeld             jlixfeld at
iDirect Network Operations   jlixfeld at

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