Questions about ICMP

[Rick Stevens]

On Wed, 2007-12-05 at 16:00 -0800, Daniel B. Thurman wrote:
> Craig White wrote:
> 
> >Sent: Wednesday, December 05, 2007 3:33 PM
> >To: For users of Fedora
> >Subject: Re: Questions about ICMP
> >
> >
> >On Wed, 2007-12-05 at 15:27 -0800, Daniel B. Thurman wrote:
> >> Should ICMP packets be allowed both over the
> >> Internet or should it be allowed to pass only in
> >> the local networks?
> >> 
> >> I have a firewall appliance and trying to make sure
> >> that I am being secured properly.
> >----
> >disabling icmp echo requests is a great feature for the ultra-paranoid
> >
> >Craig
> >
> >-- 
> 
> So... am I to read this as it is a good idea to disable all icmp
> requests?  I get a LOT of ICMP requests from the Internet probing
> at my ports, which are disabled.  This is a good idea?

There is no reason for people to ICMP you unless they're just snooping
to see what IPs are in use--and that can indicate an oncoming hack
attempt.  It is a very good idea to turn it off.

I do...at least at my router/firewall.  The Internet doesn't need to
know I'm there.  Internally I leave it enabled so I can verify my
machines are alive (that and SNMP stuff).  So if you're on my private
network, pings are OK.  I ignore attempts from the outside (in iptables
parlance, "-j DROP").

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- Rick Stevens, Principal Engineer             rstevens at internap.com -
- CDN Systems, Internap, Inc.                http://www.internap.com -
-                                                                    -
-  Silence!  Or I shall replace you with a very small shell script!  -
-                                                - The Wizard of OS  -
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