Anonymous is a group fighting in various countries like china against Censorships. They have started a new campaign for Indian government websites with the name #OpIndia.
Anonymous attacks Indian Websites
Recently few days back, Indian government has blocked access to many websites like ThePirateBay and Vimeo, similarly few days back Kapil Sibal telecom minister of India had meet up with representatives of Facebook, Microsoft and Google an discussion for screening of content on social media websites.
What is DDOS Attack
Anonymous uses an DDOS attack, according to Wikipedia
Denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer or network resource unavailable to its intended users.
You can get their live updates at #OpIndia