Yes, they spoof IPs. And they use open proxy servers. Banning IPs is a mixed bag. You might have some success if you ban entire blocks of ips that come from open proxies. But you may end up banning legitimate users that way, too.

Just to give my experience with this, in August & Sept, I was getting hit with ~100 trackback & comment spams per day. I tried banning IPs, which helped for about a day, but they'd find new addresses and continue.

I made two changes to my blog, and all the spam came to a screeching halt.

1) I updated my blog to Dawn (0.9.1)
2) I [url=http://forums.b2evolution.net/viewtopic.php?t=3764]renamed my htsrv folder[/url]
3) I removed the link to my blog's stats page

The first two are what really helped. After trying all of these methods, my opinion is that banning IPs is not a good solution for a couple of reasons. First, the spammers can get access to new IP's, so they're always going to be one step ahead in this regard. Second, you could end up blocking legitimate readers if you ban a range of IPs.

I hope this helps. And FWIW, I really appreciate the b2e community rallying behind this cause. I would have given up on my blog were it not for these forums.

Actually, I believe they aren't spoofing their addresses, but just use open proxies most of the time.

Spoofing an IP isn't that easy and can be prevented by firewalls and ISPs, as far as I know.