The 45% figure came from pulling ARIN records on every unique IP from which I received comment spam on 31 Dec and 1 Jan. Comcast has done quite a lot to stop email spam, but at least in parts of the network, but it hasn’t been enough to make a very big dent in the overall outgoing spam flow. For instance, you may find they block outgoing port 25, but do they also block port 587? I also notice they are blocking a lot of incoming ports as well now, but not quite enough. There are way too many malicious programs out there, and 65535 ports to choose from…and at some point, these blocks will start interfering with legitimate connections. Or the already-installed spambot can just contact a remote site for instructions. I know of at least one spambot that does this, making the inbound blocks ineffective.

As for captchas, I hate them with a passion, and you simply will never see one on my site. I decided moderation was probably the best route to go with such comments. Although there are still a few addresses which are blocked entirely, anyone affected can easily have their IP address removed from the block list.