The defacement was so brief as to make people wonder if it really happened, but both the company and Zone-h.com confirmed it.
Ultimately, the site wasn't compromised - the attack turned out to be a DNS hijack that made the domain point to two different IP addresses.
"The defacement was caught in minutes and corrected immediately," stated Rovio VP of Marketing Communications Saara Bergström. "The end user data was in no risk at any point. Due to how the internet name resolution works, for most areas it was not visible at all, but some areas take time for the correct information to be updated."
The attack was executed by a hacker who dubbed himself as "Anti-NSA hacker", and was apparently motivated by the recent report claiming that the US NSA and UK GCHQ have targeted "leaky" phone apps in order to collect user data. The report mentioned the Angry Birds app by name.
Rovio reacted to it by officially stating that they don't "share data, collaborate or collude with any government spy agencies such as NSA or GCHQ anywhere in the world."
"The alleged surveillance may be conducted through third party advertising networks used by millions of commercial web sites and mobile applications across all industries. If advertising networks are indeed targeted, it would appear that no internet-enabled device that visits ad-enabled web sites 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," stated Mikael Hed, CEO of Rovio Entertainment.
"In order to protect our end users, we will, like all other companies using third party advertising networks, have to re-evaluate working with these networks if they are being used for spying purposes."