Complex sentence: The hacker groups Anonymous and LulzSec claimed to have made it public on December 24,2011 as part of Operation AntiSec, however Stratfor denied that the hack recovered the client list.
Split into simpler sentences: The hacker groups Anonymous and LulzSec claimed to have made it public on December 24,2011 as part of Operation AntiSec. However Stratfor denied that the hack recovered the client list.