Re: Removing ping/icmp from a network

Tracing route to []
over a maximum of 30 hops:
1 8 ms 8 ms 9 ms flexnet-adsl-customers []
2 8 ms 8 ms 8 ms shhh.our.upstream []
3 8 ms 8 ms 7 ms
4 10 ms 9 ms 8 ms []
5 61 ms 62 ms 62 ms []
6 61 ms 62 ms 62 ms []
7 82 ms 85 ms 84 ms []
8 84 ms 83 ms 101 ms []
9 83 ms 83 ms 81 ms
10 91 ms 85 ms 83 ms []
11 83 ms 81 ms 81 ms []
12 83 ms 82 ms 81 ms []
13 81 ms 84 ms 84 ms []
14 87 ms 85 ms 82 ms
15 * * * Request timed out.
16 * ^C


----- Original Message ----- From: "Jason" <securitux@xxxxxxxxx>
To: "Mark Owen" <mr.markowen@xxxxxxxxx>
Cc: "Ansgar -59cobalt- Wiechers" <bugtraq@xxxxxxxxxxxxxxxx>; <security-basics@xxxxxxxxxxxxxxxxx>
Sent: Thursday, March 27, 2008 8:52 AM
Subject: Re: Removing ping/icmp from a network

ICMP is allowed throughout most Internet routers, if you can trace all
the way to the hop before the firewall, then you have narrowed down
where the issue is.

From there, what about network analysis and application monitoring
tools? What about tcpdump, ethereal, etc? Can that not be used that to
check network and server latency / response times on a standard web

We have a customer in Australia who's ISP blocks all ICMP to and from
their CPE routers. We seem to get along just fine. Web site is down or
is slow and the router before the CPE is responding, dump the packets,
look at the timestamps and see what's going on. IP packet traces spit
back latency just fine with or without ICMP. Problem inside the CPE?
Use remote management tools over a VPN to troubleshoot further (if you
manage the server of course).

Reputation is not going to change based on whether ICMP is allowed or
not... if the web site is down its down, clients aren't going to care
if they can ping it or not if they can't access their data through SSL
or whichever protocol either way. "Well I can't do my job, but this is
a stable server because I can ping it".

Plus, if you absolutely must have ICMP to troubleshoot from the
Internet, firewall rules can be used to narrow the source and
destination as someone else in this thread suggested. I may have given
too much of a blanket statement when saying no ICMP from the Internet
at all, I should have said no open ICMP. Controlled ICMP through a
firewall with proper rules should be good.

I don't consider MS's site unreliable just because I, or anyone on the
Internet for that matter, can't ping it.


On Thu, Mar 27, 2008 at 1:09 PM, Mark Owen <mr.markowen@xxxxxxxxx> wrote:
On Thu, Mar 27, 2008 at 12:25 PM, Jason <securitux@xxxxxxxxx> wrote:
> The idea is to limit your Internet footprint to make it as difficult
> as possible for an attacker. There is no need for a web server to
> respond to ping from the Internet for example.

It is very critical that your web server responds to ICMP on the
Internet. If you go out of the way and ignore essential protocols for
IP over a public network, you're just going to create a headache for
all of us.

Without ICMP, it is very difficult for us to determine where a problem
exists when our clients complain about slow load times or
inaccessibility to your website. No ICMP means no basic trace
routing, no basic latency checks, and no basic error reporting. So
even if the problem is somewhere in our infrastructure that limits or
prevents access to your site, you're going to get the blame and bad
reputation of an unstable server. If it doesn't respond to ping, and
can't be traced, its not our fault that our client can't access your
site, it's yours.

Mark Owen