On January 26, the website for Malaysia Airlines was hacked and defaced with pro-ISIS messages. The hackers claimed to be part of the hacker group Cyber Caliphate, which has already carried out a number of attacks, including hacking the Twitter and YouTube accounts of U.S. Armed Forces Central Command (CENTCOM). However, it subsequently became apparent that the hackers were actually part of the Lizard Squad, a hacker group that recently made headlines by hacking Sony and Microsoft's online gaming services. The initial defaced page that claimed responsibility for Cyber Caliphate was eventually replaced by one from Lizard Squad (as seen above).
Initial defacement that claimed to have been conducted by Cyber Caliphate:
Tweets by Lizard Squad confirming the hack: