The BBC have activated a protection mechanism on the Flash based streaming system used by iPlayer, stopping open source media players from legally playing BBC content. The protection mechanism, known as SWF Verification, sends a "ping" message to the player software after one or two minutes of a stream being played. The player software is expected to identify the Flash version in use; if it does not, or if it's response doesn't match a list of authorised players on the server, then the stream is disconnected. Previously, iPlayer had not sent SWF Verification pings, and media players such as XBMC were able to include open source plug-ins which could play the content. Now, these plug-ins stop working after one or two minutes.