Twitter and Spotify are among a host of websites hit by a cyber attack that has disrupted service for many users around the world.
A distributed denial of service (DDoS) attack on domain name system provider Dyn has left many users - predominately in the US - unable to access services also including SoundCloud, AirBnB and Reddit.
A DDoS attack is when a website is flooded with traffic until it can no longer support it and is forced offline.
As Dyn is part of the support network of a number of major sites, the issue has quickly spread to a number of popular service.
The attack was first reported on website Hacker News, which named social media giant Twitter along with music service Spotify among a list of "sites down", though users in the UK have been mostly unaffected by the issue, with reports suggesting those based in the north-east US have been worst-hit.
Security experts have labelled the attack a "nuisance" but warned the style of attack can sometimes be used as a diversion from other activity.
Mark James, from cyber security firm ESET, said: "DDoS seems to be more widely used these days to cause disruption and nuisance.
"DDoS, of course, may not only be used to make a statement or bring voice to your protests, it may and has on many occasions been used as a smokescreen to cover other nefarious purposes, which may include data theft or malware infection.
"We all need our daily fix of the digital programs that are so intertwined into our daily lives and when those services are down we tend to get a little edgy.
"I'm confident the tech teams involved will be working as hard as they