Things to do to make the network better

Tom Killalea tomk at
Mon Jan 5 17:56:43 UTC 1998

>I will also point out that many of the recent "smurf" attacks and
>similar problems people are having on the net would be gone if people
>would just carefully filter internal/external addresses on their
>border machines, that is, prevent packets claiming to be from "inside"
>networks from coming in from the "outside", and prevent packets
>claiming to be from "outside" networks from going out from the
>"inside". The latter will stop your network from *ever* being the
>source of a wide variety of packet forgery attacks, and is necessary
>to being a good network citizen. The former will stop your network
>from being the subject of a wide variety fo packet forgery attacks,
>and is necessary to make your customers even remotely safe on the net.

I strongly recommend such filtering in sections 5.7 and 5.8 of my 
"Security Expectations for Internet Service Providers" draft
and we've heard Paul plug
here many times.

To answer Owen comments regarding the difficulty of filtering for
transit providers, I argue that filtering should happen as close to the
actual hosts as possible.

Tom Killalea   (425) 649-7417    NorthWestNet
               tomk at

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