Federal authorities shut down one of the Web’s most popular sites Thursday on charges that it illegally shared movies, television shows and e-books, prompting hackers to retaliate by blocking access to several Web sites, including those of the Justice Department and Universal Music.

The shutdown of Megaupload was part of a federal indictment accusing the company of running an international criminal organization that allowed consumers to easily watch or share pirated content. The site’s offerings were a virtual bazaar of what the Internet has to offer, including pornography and illegally copied video games, federal officials said. In some cases, people could see movies before they were released in theaters.