-The RIAA hires unlicensed investigators to put fake files on p2p sites(Illegal)(Entraptment??)...So when u download a fake it says your ip address an they nail you with an infringment notice through your internet provider...
-They may sue you as well...Many lawsuits are settled because the RIAA scares you with hundred thousand dollar penalties..Most settle out of court..Love that legal extortion!