A company callled MediaSentry revealed some of their methods in a Canadian court case about file sharers' ID's last year

Quote:

Mr. Millin also testified that his company provided a service called MediaDecoy which distributes bogus or inoperative files over the internet. People downloading these files think incorrectly that they are music files. The files are made to look like real music files, but they are inoperative. When he was asked whether he could tell whether any of the files allegedly copied from the alleged infringers were MediaDecoy files, Mr. Millin stated that he had not listened to any of the files copied from the alleged infringers and that listening to the files was not work that his firm was contracted to do or the “process that we set up with CRIA” (Millin cross-examination, QQ 107-107, 189-196). This kind of remote evidence in no way qualifies under Rule 81. There is, thus, no evidence before the Court as to whether or not the files offered for uploading are infringed files of the plaintiffs.

from the decision "T-292-04.pdf" available at http://www.cippic.ca/en/projects-cas...ring-lawsuits/