The Website 'www.bsnl.co.in' was quickly restored.
The group Anonymous India said that it hacked the Website in support of activists Aseem Trivedi and Alok Dixit, who are on a hunger strike to protest Section 66A of the IT Act.
"Our website has been hacked and our people are working on it," BSNL Chairman and Managing Director R K Upadhyay told PTI.
The site has since been restored.
The Twitter account of Anonymous India (@opindia_revenge) said, "BSNL Websites hacked, passwords and database leaked http://pastebin.com/wjtiyvx4 Anonymous India demands withdrawal of Sec 66A of IT Act."
Trivedi and Dixit are on a hunger strike for the last six days in protest against Sec 66A of IT Act.
Facing public protests on the recent controversial arrest of some persons for their Facebook posts using the section 66A of IT Act, Government last month came out with guidelines where a police officer no less than the rank of DCP can sanction prosecution.
The guidelines were being issued after controversial arrests by Mumbai police under Section 66 (A) of Information Technology (IT) Act that deals with spreading hatred through electronic messages.