So, the spammer is using a tripod domain, therefore a complaint can be lodged with tripod.com because it's a breach of their AUP. They'll have a record of the subscribers IP address, and aside from reviewing their own sign-up process, they'll have an idea of "what pool" of IP's the spammer is hiding behind and can make that information available to the FBI so the route can be traced back to the originating IP. If it's a bot attack, they came from "somewhere" and unless the spammer has invented a brand new trick, that person will eventually be discovered.
But a complaint needs to come from the owners of this domain for it to be followed up by the proprietors of tripod, whom can probably do without the headache of potential litigation so I'm sure they'll be quick to act.
You can try contacting them at:-
Tripod is owned by Lycos, Inc