A hackers group going under the handle of Anonymous with Twitter handle of @AnonyInfo today claimed that they were able to hack into following sites.
1: Pentagon
2: New York Times
3: US Army
4: Spam List FBI, DOJ LAPD
Anonymous hack Pentagon, NY Times, US Military and leak email ids and phone numbers
They have not only claimed to hack the above websites but released a proof of concept of the method they used to hack it. You can read it here.  The hacker have tweeted that this hacks were done under a operation called #AntiSec Operation.  #AntiSec or Operation AntiSecurity is a operation which was started by a group called LulzSec and Anonymous and later on others inspired by it joined the operation. 

LulzSec performed the first of the hacks under this operation when on 20th June, 2011, they took down the Serious Organised Crime Agency. Later they went on to leak the information taken from the servers of the Arizona Department of Public Safety. At a later date, Anonymous too hacked the same agency twice and again released information often embarrassing the US authorities.   An offshoot of the group calling themselves LulzSecBrazil launched attacks on numerous websites belonging to the Government of Brazil and the energy company Petrobras. 

LulzSec then posted a news of the retirement of their group but emerged later to hack into the websites of websites of British newspapers The Sun and The Times, posting a fake news story of the death of the publication’s owner Rupert Murdoch.  

However this latest hack has been confirmed to be conducted by AnonyInfo as well as LulzBoat as per these tweet.

#AntiSec – The Pentagon https://t.co/Jozd6LkQdQ#LulzSecurity in your servers
— The Lulz Boat (@LulzSecurity_EU) March 22, 2014

No way, we pwned the Pentagon AGAIN? LEAKED: https://t.co/BdjrQQnDDp https://t.co/HrBTSPHJ9s #Anonymous #AntiSec
— Anonymous (@AnonyInfo) March 22, 2014

The pastebin has over details of over 150 personnel working for Pentagon alongwith their email ids and phone numbers.  They have also published hundreds of login ids and passwords as well as cracked hashes.

The hackers also claims that this is not the end and they will leak documents from BioTech 

No way, we pWneD the Pentagon again?Yes Sir we did!This ISN’T our mainLeak this week our main leak willbe our biotech leak!!But whatever pentagon informations still epic

while there is no proof that the leak is legit. few believe that it may come from the old leaks, what now everyone is looking for is the biotech leak which can help to identify how legit these leaks are.