The outage lasted for about three hours.
You may have taken to Twitter to complain about it, or research it, and saw people talking about how Xbox Live was hacked by the hacking group Anonymous.
That's because while Xbox Live was down, Anonymous tweeted that they had hacked the gamer network and stole a bunch of gamer data.
#XboxLive now belongs to us. All online gaming data will be seized by Anonymous. #XboxLiveDown
- Anonymous (@TheAnonMovement) January 29, 2015
Anonymous also tweeted that they took Xbox down by blocking access to the site, through what's known as "distributed denial of service" attack (DDoS). A DDoS attack is when a hacker controls many computers all over the Internet and tells them to access a website at the same time, overwhelming the site with requests and bringing it down.
Anonymous is actually DDoSing Xbox Live. #Anoymous was made for "Teh Lulz". We do fight for people around the globe, but we also troll. :)
- Anonymous (@AnonEnvironment) January 29, 2015