What he probably does is called "sewer service" where he gets a document server to fill out and affidavit stating that you were served the complaint/subpoena. You then never get the paper work and the trial date happens and you don't show up and lose by default. He can then get the sheriff to garnish your wages and take whatever property and money you have in the bank.

The easy way to fight this is as soon as you've found out there is a judgment against you, go to court and file a motion to vacate pending a new trial because you were never served the papers. The judgement is then thrown out and a new court date set.

At this point get a lawyer and file for discovery to see exactly what he has against you. Usually and since these people are scam artists, they won't have the needed paperwork to prove injury and won't have any standing in the court.

Whereas it pertains to copyrights, under the DMCRA, he has to show he's given you written communication to cease and desist and you refused. This proof is usually a certified letter postmarked by the post office.

Whatever you do, once you find out there is litigation against you do not ignore it! These scammers are depending on your to not show up to court and present you defense. But you can beat these guys and even counter sue them for misuse of the court if push comes to shove.