The website of the British state broadcaster was down for a number of hours on New Year's Eve
A group that managed to take down the BBC website on New Year's Eve says it was only running a test.
New World Hacking says its main aim is to block sites hosting Islamic State propaganda.
All BBC pages were out of action for several hours after being deliberately flooded with traffic.
A member of the apparently US-based group spoke to BBC technology correspondent Rory Cellan-Jones via Twitter, saying they carried out distributed denial of service - or DDoS - attack to "see our actual server power".
The representative added that while their actions are "not always the right choice", the group is engaged in cyber hacking because "who is there to fight off online terrorists?".
BBC said the outage - which affected the main BBC website as well as services such as the iPlayer video streaming app - was the result of a 'technical issue'.