Social media sites, including Facebook and Instagram, were briefly unavailable on Tuesday morning around the world, with a hacking group called the Lizard Squad claiming responsibility for the outage.
Both desktop and mobile sites were affected and the issue latest around an hour. Chat app AIM and dating app Tinder were also affected, according to reports.
There was speculation that the social media sites had been hit by a type of cyberattack called a distributed denial-of-service attack (DDoS), which is designed to slow down a website's user experience. A Twitter account which claimed to be associated with Lizard Squad posted a message saying it was behind the attacks.
However, Facebook denied that the outage was because of a cyberattack.
"Earlier today many people had trouble accessing Facebook and Instagram," a company statement, emailed to CNBC, said.
"This was not the result of a third party attack but instead occurred after we introduced a change that affected our configuration systems. We moved quickly to fix the problem, and both services are back to 100 percent for everyone."
DDoS attack?
Lizard Squad has claimed responsibility for defacing the Malaysia Airlines website on Monday, although the airline has denied that this is the case. On Tuesday, the group appeared to threaten to publish information stolen from Malaysian Airlines online.
Matt Navarra, a social media director from technology website thenextweb.com, told CNBC via email that Tuesday's social media outage did "initially" look like a DDoS attack, but that it was too early to tell for sure.
"While it's inconvenient for users and frustrating for Facebook and other services that went down, it's fairly unlikely that user data has been exposed," he said.
David Emm, principal security researcher at the internet security group Kaspersky Lab, told CNBC via email that DDoS attacks were nothing new and had been a threat for many years.
"(They) are one of the most popular weapons in a cybercriminals' arsenal. However, we're seeing the level of danger from these attacks increasing," he said. The latest research from Kaspersky Lab showed that 38 percent of companies providing online services had fallen victim to a DDoS attack in the last 12 months.
"The problem is that today DDoS attacks can be set up cheaply and easily, from almost anyone, whether that be a competitor, a dismissed employee, socio-political protesters or just a lone wolf with a grudge," Emm added.
Brief outage
Just after 6 a.m. GMT, attempts to access Facebook brought up an error message telling users that "something went wrong" and the company was working on fixing the problem. The problem was resolved at 7.10 a.m. GMT.
Meanwhile, Instagram - a photo uploading site that is owned by Facebook - went to a blank page on a desktop computer and the mobile application failed to load new posts.
Instagram said on rival social media site Twitter at 6:51 a.m. GMT that it was aware of the outage and was working on a fix. "Thank you for your patience," it said in a message to its followers. The tweet was removed after the issue was resolved.
During the blackout, disgruntled users took to Twitter - which was working as normal - to vent their frustration at Facebook, which for many people has been a part of their everyday lives since its formal launch in 2006. Others used the microblogging site to poke fun at the situation.
Earnings due Wednesday
Facebook, led by CEO and founder Mark Zuckerberg, is due to report it fourth-quarter and full year earnings for 2014 on Wednesday.
It is not the first time that the world's largest social network, has experienced wide-spread interruptions.
Brief outages have occurred in recent years, but the most notable was in 2010. Facebook stated on its website that it was—at the time—the "worst outage we've had in over four years." It lasted for 2½ hours and was caused by an "unfortunate handling of an error condition."
In June last year, Facebook was briefly unavailable for 30 minutes, with users once again unable to log in. Reports from news wires at the time indicated that users from all over the world had been hit by the outage.