[nsp] known networks for broadcast ping attacks

Wed Jul 30 21:20:00 UTC 1997

> The real problem I see with this particular attack is that there is 
> nothing short of blocking all ICMPs that 'victim.com' can do. At least 
> not that I am aware of.

Well, I've been filtering ICMP for quite a while at my border routers, 
and other than the occasional braindead sendmail configuration, and
the fact that Solaris ping can't handle the "Administratively prohibited" 
return from the IOS filter rule, I've yet to see a major downside.

We have a very large quantity of people hitting our network every day.

Is there a specific reason that you can see to allow ICMP inbound to 
a 'victim.com'?  Or at least to more than a handful of specific 
addresses?  Perhaps there's a better solution with some sort of ICMP 
"proxy" at or just behind the router?

Paul
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Paul D. Robertson
gatekeeper at gannett.com