I actually think the tool(s) are free to the users of phpBB.
Implementation is the tricky and timely part
It is really rampant though on here. I haven't ever really seen it happen like this before(not a IT guru just a multi-forum user ).
DDH uses captcha as well to limit spammers from getting an ID, but even the spammers have bot tools to beat captcha.
I think an ip address track would maybe show the IP addresses coming from the same country (call me crazy but i'm gonna go with China)
Block these ISP's too telefonica.com.ar,unicom-cn, ovh.net ,telecomitalia.it, chinanet-zj, hinet.net ,unicom-hl ,iliad.fr,shawcable.net ,telefonica.com.br
"Go as far as you can see; when you get there, you'll be able to see farther."