Facebook and Instagram are widely popular among users around the world to connect with a large community of friends and family with a single post. But both these platforms, along with Facebook's Messenger app, went offline for a brief period on Monday, putting millions of users through a digital detox.

According to Downdetector website, the outages on Facebook, Instagram and Messenger were not widespread, but largely affected the north-eastern United States, California and the UK. Users were unable to login, refresh feeds or experienced a total blackout. The outages lasted about an hour, and all Facebook-owned services are working normally as of this writing.

But the biggest question lingering in the minds of users and some privacy advocates is what caused the popular social networking services to go offline. There were speculations that Facebook's servers were attacked and the services were disrupted due to this. But a hacker group has stepped forward to claim responsibility for the outages.

Facebook logo
Facebook went down briefly on MondayREUTERS/Dado Ruvic

Lizard Squad, black hat hacking organisation, claimed responsibility for Facebook, Instagram and Messenger outages.  The hacker group tweeted on Monday, saying "try sending a message through Instagram."

The attack, which could be a DDoS (distribution-denial-of-service attack) overloaded Facebook servers, which caused the outage. Users were unable to send messages on Messenger, share posts on Instagram and Facebook.

Twitter was flooded with complaints about Facebook, Instagram and Messenger outages. The services were restored shortly after, which was a relief to many who had experienced a massive outage back in March.

WhatsApp and Facebook messenger icons seen on iPhone
Facebook, Instagram, Messenger were offline on Monday, here's what happenedREUTERS/Phil Noble

Facebook is yet to release a statement regarding Monday's outages. The social networking giant has had too many instances of outages that left millions of users cribbing and complaining. In September, Facebook and Instagram were down in the UK and some parts of Europe. But the biggest outage affected Facebook, Instagram and WhatsApp in March, which rendered the platforms inaccessible for more than 14 hours.

At the time, Facebook blamed the outages on database overload during "server configuration change", which overwhelmed the servers. After several hours of maintenance and repair, Facebook was able to restore all services, but it raised questions on Facebook's ability to fix problems.