Microsoft has reportedly started censoring links to infamous BitTorrent site The Pirate Bay shared through its instant messaging service, Windows Live Messenger.
The issue was first flagged up by TorrentFreak, which found that users who tried to paste a Pirate Bay link to their friends through Windows Live Messenger were met with a message stating that the link had been blocked because it was "unsafe".
Other chat clients such as Pidgin are also blocking Pirate Bay links when accessed using a Windows Live Messenger account.
Microsoft was contacted by Techworld for comment, but did not reply in time for the publication of this article. However, the company told The Register:
"We block instant messages if they contain malicious or spam URLs based on intelligence algorithms, third-party sources, and/or user complaints. Pirate Bay URLs were flagged by one or more of these and were consequently blocked."
The move has been interpreted as an indication that Microsoft is joining the fight against online piracy. However, as TorrentFreak points out, all of the other large BitTorrent sites remain unaffected, even though they offer identical content.
It is nevertheless a blow for The Pirate Bay, which has been the target of numerous legal challenges in recent months. In February, the High Court in London ruled that The Pirate Bay breaches copyright laws, meaning that the site could be blocked by internet service providers in the UK.
Meanwhile, Finnish ISP Elisa has blocked access to The Pirate Bay in response to an injunction issued by a Helsinki court at the request of the International Federation of the Phonographic Industry, and a court in The Hague has also ordered that The Pirate Bay must be blocked by Dutch ISPs Ziggo and XS4ALL.
Earlier this year, The Pirate Bay announced it will no longer host torrent files, opting instead to use magnet links, which are more difficult to track and shut down.
Mr Justice Arnold, who oversaw the High Court hearing, said this confirmed the operators' determination to do whatever they can to provide users with unrestricted access to copyrighted material and thereby enable the users to continue to infringe.