Cerberus Network is an online DLC and news service for Mass Effect 2.
It is available for free with every new copy of Mass Effect 2 or for separate purchase at a cost of 1200 Microsoft Points (Xbox 360) or 1200 BioWare Points (PC).
It can be accessed from the Mass Effect 2 main menu, and is seen as a terminal display for news and updates. On the main Mass Effect 2 start screen, there is a second computer on the right-hand desk that opens to show the Cerberus Daily News and any new DLC that is available. Most Cerberus Network DLC is free, and the only charge that could be applicable is if the copy of Mass Effect 2 isn't new.