On Tue, 24 Nov 2009 16:38:33 EST, Brad Laue said: > True, but wouldn't a blacklist of SPF records for known spam issuing > domains be a more maintainable list than an IP block whitelist? > > (I'm no doubt missing something very obvious with this question)
140M+ .com where a malicious DNS server in East Podunk can be authoritative for a domain actually in Bratslavia and domains are cheap and throw-away. 16M /24's, where you (mostly(*)) need to be able to actually route the packets, so if you have a /24 in Bratslavia, you need something resembling a router in Bratslavia as well, and somebody willing to light up the other end of the cable, and you need a way to make BGP announcements (legal or otherwise ;) to be able to exploit it. Choose wisely which you'd rather use for defense. (*) Mostly - though the BGP hack demonstrated at last year's DefCon did qualify as an Epic Win for kewl presentations. ;)
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