An appeals court in the Netherlands has thwarted attempts by the anti-piracy organisation BREIN to get the identities of file-sharers from five ISPs.

BREIN used MediaSentry to link the files with user's IP addresses, a practice which came under fire from expert testimony as well as the Dutch court.

MediaSentry's software has been widely criticized for being too limited and simplistic, taking filenames at face value and violating the legally protected privacy of users in some countries by "scanning" entire shared directories of specific users.

The court found that the manner in which IP addresses were collected and processed by US company MediaSentry had no lawful basis under European privacy laws.

BREIN represents 52 media and entertainment companies that have been investigating 42 individuals suspected of swapping song files. Nine individuals have settled out of court with BREIN choosing not to fight a costly and legthy legal battle.