In some mail from Ryan Russell/SYBASE, sie said:
> The person who posted the question was under the impression that SPF couldn't
> but proxies could. I believe that neither can effectivly protect from that
> type of attack,
> because it requires very specific knowledge about the platform in question on
They both `can'.
But, in both cases, you must somehow put the knowledge about what is good
and bad in the proxy/filter code.
It doesn't require any knowledge about the interior platforms which it is
attempting to protect.
How it is implemented is purely an implementation issue.