Games for the PlayStation 2 that were produced without the permission or knowledge of Sony.
The console has rigorous copy protection, but the producers of these discs pressed the authentication data from legitimate games onto their discs, circumventing this. A blacklist in the mechacon contains a list of the aforementioned discs' fingerprints (unique properties to the data, like a file hash). Manufacturers of unlicensed discs attempted to circumvent this by releasing newer versions of the discs, which would subsequently be blacklisted again.