On 14 November 2015 Anonymous posted a video announcing its "biggest operation ever" against the terrorist group in response to the attacks in Paris, taking down 3,824 pro-ISIS Twitter accounts and doxxing recruiters. A message posted by an ISIS-affiliated account on encrypted chat service Telegram replied defiantly to Anonymous by providing instructions on how to respond to a potential cyberattack. On 25 November, an ISIS WordPress dark web site was reportedly hacked by GhostSec, which replaced the site with an advert for Prozac.