A hacker group called Lizard Sqaud have said they were responsible for Facebook, Instagram and Tinder going down.
Users around the world tweeted about issues with the services before normal service resumed.
The group also took responsibility for an attack on the official website of Malaysia Airlines the previous day.
Lizard Squad claimed to be behind a series hacks of Microsoft and Sony gaming networks over Christmas as well.
Earlier this month, A UK man was arrested as part of an investigation into denial-of-service attacks on Playstation and Xbox systems.
The 18-year-old from Southport is accused of unauthorised access to computer material and knowingly providing false information to law enforcement agencies in the US.
So who are they and what could be next?
Who, or what, is Lizard Squad?
A hacker claiming to be from Lizard Squad – a 22-year-old calling himself Member Two – said the group had hacked the sites “because we can”.
He also suggested the motive was to demonstrate weaknesses in the Microsoft and Sony systems.
“It’s just such a huge company Microsoft… Do you not think they should be able to prevent such an attack?” he told BBC Radio Five Live.
“Is Christmas really about children playing with their new consoles, or playing with their new toys, or is it about them spending time with their families and celebrating Christmas?” he added. “I think everyone’s just taking it all out of the ordinary.”
The name Lizard Squad is generally used as a signature on a site that the group has taken responsibility for hacking.
A previous attack on gaming and media streaming site Machinima, Inc. names Criminal, Jordie, Pain and Plague as the hackers.
The majority of Lizard Squad’s online activity, outside hacking, comes via their Twitter account.
Many posts taunt recent targets or promise upcoming hacks.
What has the group done before?
The Christmas gaming take-down is is the latest in a string of hacks Lizard Squad claims to be behind.
Recent high-profile targets which the group has taken responsibility for taking offline include EA games, Destiny, Xbox Live at the beginning of December.
A series of Twitter posts from Lizard Squad, shared a few weeks ago, included threats that said they intended to target Xbox Live over the festive period.
“Microsoft will receive a wonderful Christmas present from us,” they wrote.
Sony’s PlayStation Network was also hacked in August.
The attacks coincided with a bomb scare involving a flight carrying a Sony executive.
An American Airlines jet was diverted after a threat was made online.
They’re not the firstAlthough Lizard Squad are making headlines at the moment, other hacking groups have targeted high-profile sites.
Earlier this month a different branch of Sony – Sony Pictures Entertainment – was hit by a cyber attack that stole huge amounts of data from its servers.
The fallout from that hack soon focussed on The Interview, a film featuring a fictional plot to assassinate North Korea’s leader Kim Jong-un.
In April last year, four British hackers who were behind a series of high-profile cyber-attacks in 2011 were given jail sentences.
Ryan Cleary, Jake Davis, Mustafa al-Bassam and Ryan Ackroyd were part of the Lulzsec hacking group, which targeted sites including Sony Pictures, News International, the CIA and the UK’s Serious Organised Crime Agency.
The following month, Australian police said they had arrested the 24-year-old “self-proclaimed leader” of the hacking group.