&quot;The problem isn&#x27;t unique to Tor. It&#x27;s anything that allows a spammer to use the same IP address as innocent people, including things that aren&#x27;t exactly legal, like compromised PCs and routers. &quot;<p>That&#x27;s <i>sort of</i> true. It&#x27;s technically true that any I.P. address might be the source of malice. Yet, Tor&#x27;s I.P. addresses will <i>steadily</i> be the source of a <i>ton</i> of malice with <i>no resolution</i> of that problem. Quite different than what happens when someone&#x27;s ISP tells them there&#x27;s malware on their machine. There&#x27;s also economics involved where people have to pay for those machines and are therefore more likely to use them for other, profitable activities. Probably why we see less spam from those accounts.<p>What remains are WiFi hotspots, libraries, etc. Apparently, they&#x27;re not drowning services in hatemail and spam because they&#x27;re still allowed. They <i>could</i> but few are complaining about them.<p>&quot;And the problem is going to get worse as a result of IPv4 address exhaustion because some ISPs are going to have to start using carrier grade NAT (and some already are). &quot;<p>Good call. I saw this coming. There were already talks by Ross Anderson IIRC about how critical it was for forensics to get the port number and time-stamp since CG-NAT would make I.P.&#x27;s useless. Already is in some areas.<p>&quot;So the thing to show for it is that you can field test your solution prior to the day of Spam Armageddon when a spammer realizes they have a botnet with access to a million billion IPv6 addresses.&quot;<p>Haha. Interesting way of looking at it. I&#x27;m more worried about the routing tables, though, if IPv6 got massive surge of traffic. Never looked to see if they fixed early concerns about how well Tier 1-3 HW would handle it vs IPv4.