Re: New Denial of Service Attack on Panix

["Perry E. Metzger" <perry () piermont com>]

"Forrest W. Christian" writes:
> Maybe I'm missing something here, but wouldn't these Denial of Service 
> attacks cause a severe mismatch in the numbers of SYNs and SYN-ACKs on a 
> given router interface?
[...]
> Then, if the ratio got too high, it can start yelping about "Potential SYN 
> D-O-S Atttack in progress on Interface Serial 1"
>
> In this manner "good" isp's wouldn't unknowingly carry these attacks.

I think it is easier to just block the attacks completely by source
filtering your own network, at which point you can't carry such an
attack, knowingly or unknowingly.

> I envision this being done on the somewhat bigger isp's where
> putting inbound filters on their customer interfaces would be not a
> good idea (Sprint, MCI, Net 99, etc.).

What you propose is actually much harder to build than filters are.

> Personally, I know that these attacks aren't going to originate at our 
> site, as I have the filters on.   However, I am quite concerned about 
> getting hit with one...

Please help, then, in convincing people that it is important to turn
on filtering on all leaf networks.

Perry
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