The official Angry Birds website was defaced by hackers following reports that U.S. and U.K. intelligence agencies have been collecting user information from the game and other popular mobile apps.

Some users trying to access the www.angrybirds.com website late Tuesday were greeted by an image depicting the Angry Birds game characters accompanied by the text “Spying Birds.” The U.S. National Security Agency’s logo was also visible in the image.

The NSA and Britain’s Government Communications Headquarters (GCHQ) have been working together to collect geolocation data, address books, buddy lists, telephone logs and other pieces of information from “leaky” mobile apps, The New York Times reported Monday based on documents provided by former NSA contractor Edward Snowden.

Mobile apps commonly collect data about their users and share it with advertising networks, which then use the information to build user profiles for targeted advertising.

A secret 20-page GCHQ report from 2012 contained code needed to extract the profiles generated when Android users play Angry Birds, The New York Times reported. It’s not clear if and how this data collection happens, but the reports were apparently enough to anger some hackers.

Yet another DNS attack

The defacement of the Angry Birds website seems to have been the result of a DNS (Domain Name System) attack where the site’s name servers were swapped with others under the attackers’ control.

’’The defacement was caught in minutes and corrected immediately,” said Saara Bergström, vice president of marketing communications at Rovio Entertainment, the Finnish company that develops Angry Birds. “The end user data was in no risk at any point.”

Bergström said the attack was similar to the one against The New York Times last year, referring to an incident where attackers pointed the nytimes.com domain to a server they controlled by changing its DNS settings.

"Rovio does not allow any third party network to use or hand over personal end-user data from Rovio’s apps."

Because of how DNS changes propagate on the Internet, the incident was only visible to some users.

In many areas the attack was not visible at all, but in some affected areas it might take time for the correct information to be updated, Bergström said.

This delay is caused by how DNS resolvers—servers that resolve domain names to IP (Internet Protocol) addresses—cache records. Some servers might cache the information for a particular domain for a longer time than others, in which case changes won’t be visible to users that rely on those servers until the cached record expires.

A copy of the angrybirds.com defacement can be viewed on Zone-H, a website defacement archive. It is attributed to a hacker using the handle Anti-NSA.

Angry ads?

Rovio issued a statement Tuesday on its website denying that it collaborates or shares data with any government spy agencies.

“The alleged surveillance may be conducted through third party advertising networks used by millions of commercial websites and mobile applications across all industries,” the company said. “If advertising networks are indeed targeted, it would appear that no internet-enabled device that visits ad-enabled websites or uses ad-enabled applications is immune to such surveillance. Rovio does not allow any third party network to use or hand over personal end-user data from Rovio’s apps.”