The Anonymous have created a Paste alleging that they have brought down atleast 18 websites belonging to the US military services under the Operation Payback which is also known “Operation: Payback Is A Bitch”. The Operation Payback, for your information, is a old operation undertaken by the Anonymous from September 2010 through to January 2011. Though the operation had been a success from Anonymous point of view but FBI had cracked hard on this operation and Anonymous in general and arrested around 13 members of Anonymous at that time.
However the latest operation seems to be directed against United States Army, Air Force. Marines and Navy. The list of websites being claimed to be brought down under this operation by Anonymous are as follows :
The paste here has been put up by YourAnonNews, a feed of the Anonymous hacktivists but it fails to give the reasons for resurrecting the Operation Payback.