The move follows a landmark High Court order on October 14 2011, which allowed the Motion Picture Association to impose blocks via BT on the members-only pirate website.
BT told the BBC that the block had come into force on 2 November and is based on software developed to prevent users from finding websites showing images of child abuse.
But a Newzbin2 work around could be allowing site members to slip in under the radar.
"Newzbin have offered their customers ...
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