On 10/1/2015 11:44 PM, Mark Andrews wrote:
IPv6 really isn't much different to IPv4. You use sites /48's rather than addresses /32's (which are effectively sites). ISP's still need to justify their address space allocations to RIR's so their isn't infinite numbers of sites that a spammer can get.
A /48 can be subdivided into 65K subnets. That is 65 *THOUSAND*... not the 256 IPs that one gets with an IPv4 /24 block. So if a somewhat legit hoster assigns various /64s to DIFFERENT customers of theirs... that is a lot of collateral damage that would be caused by listing at the /48 level, should just one customer be a bad-apple spammer, or just one legit customer have a compromised system one day. Conversely, if a more blackhat ESP did this, but it was unclear that this was a blackhat sender until much later.. then LOTS of spam would get a "free pass" as individual /64s were blacklisted AFTER-THE-FACT, with the spammy ESP still having LOTS of /64s to spare.. remember, they started with 65 THOUSAND /64 blocks for that one /48 allocation (Sure, it would eventually become clear that the whole /48 should be blacklisted). other gray-hat situations between these two extremes can be even more frustrating because you then have the same "free passes" that the blackhat ESP gets... but you can't list the whole /48 without too much collateral damage. SUMMARY: So even if you moved into blocking at the /64 level, the spammers have STILL gained an order of magnitudes advantage over the IPv4 world.... any way you slice it. And blocking at the /48 level WOULD cause too much collateral damage if don't indiscriminately. And this is assuming that individual IPs are NEVER assigned individually (or in smaller-than-/64-allocations) . (maybe that is a safe assumption? I don't know? regardless, even if that were a safe assumption, the spammers STILL have gained a massive advantage) -- Rob McEwen +1 478-475-9032