The computer hacker group Anonymous attacked websites of Brazil's federal district Saturday as well as one belonging to a Brazilian singer to protest the forced closure of Megaupload.com.
Anonymous posted messages on Twitter describing attacks against hundreds of Brazilian sites that share the URL 'df.gov.br,' which are owned by the government of the federal capital in Rio de Janeiro.
The Federal District press office denied Saturday that the hackers succeeded in shutting down the websites.
The Internet news site G1, owned by television network Globo, confirmed the early morning computer attacks but said the Federal District's 24-hour-a-day information technology team was able to stop them.
However, the hackers did succeed in shutting down the website of popular Brazilian singer Paula Fernandes. They posted the image of a grim-faced joker with a message saying, "If Megaupload is down, you are down too." It was signed "GhostofThreads."
Megaupload is a file-sharing service company that allows customers to upload files to a website, where their information can be downloaded by other Internet users. The US Justice Department shut down the company's website on January 19 after its owners were indicted on copyright infringement charges.
Hong Kong-based Megaupload has over 150 million users and 50 million visitors per day, or 4% of all global Internet traffic.
The site is responsible for "massive online piracy" that generated "more than $175 million in criminal proceeds" and caused "more than a half-billion dollars in harm to copyright owners," the FBI and US Justice Department said in a joint statement.
Anonymous -- a group of loosely organized computer hackers scattered around the world and represented by the joker face in white mask and black sarcastic smile -- is known for "denial of service" attacks on websites to protest certain government policies.
Their attacks this week, which they call "hacktivism," shut down the websites of the FBI and US Justice Department for several hours to protest the closure of Megaupload.com.
On Friday, Anonymous also briefly attacked the website of the French presidency after French President Nicolas Sarkozy said he welcomed the decision of a US federal court to shut down Megaupload.com.
Explore further: Review: Google music plan solid, serendipitous