[AusNOG] network security Question

[Colin Stubbs]

ICMP is more than just echo requests and replies or "ping" as so many think
of it.

If you're dropping unreachables and time exceeded error messages odds are
your network won't work at all, or the apps on top will perform badly while
experiencing intermittent problems.

With respect to "ping" I would deny echo request from untrusted zones to
anywhere, deny echo reply to untrusted from anywhere, but allow echo
request from trusted to anywhere with echo reply from anywhere to trusted.

You could do something similar with ICMP traceroute if you want to. UDP/TCP
traceroute must be permitted by firewalls along with letting the ICMP TTL
exceeded and unreachables pass unhindered.

Make sure you understand ICMP types and sub types before you go trying to
enforce any policy changes.

http://en.m.wikipedia.org/wiki/Internet_Control_Message_Protocol

Policy based on geographical source,  e.g. "i don't trust China and have no
need to communicate with Russia" is increasingly common in enterprise...
Not exactly feasible in service provider land.

Sent from a mobile device. Correct spelling and accurate use of grammar is
unlikely to have occurred.
On 20/05/2014 1:37 pm, "Alex Samad - Yieldbroker" <
Alex.Samad at yieldbroker.com> wrote:

> Hi
>
> Wondering what people do around
> 1) letting through icmp
>
> I like the idea of allowing icmp through, make network diagnosis a lot
> easier, but I don't want to be bomb.
> What sort of rate limiting do people think is acceptable?
> What's acceptable from client to confirm connectivity?
>
>
> 2) blacklisting ip's
>
> So I have (like a lot of others),  people port scanning look for open
> ports, what sort of levels do people actually do something about it ?
>
> I asking as an end user, but I am also curious to know what providers do.
>
> I have heard of companies blocking entire ranges, for example say china
> and/or Russia as they have no clients there. Do people do that, do ISP
> provide that service (can that be done through the auto black hole
> mechanism ?)
>
>
> Alex
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