Wikipedia is down across the globe after a 'malicious attack' - with work underway to solve the problem.
A major DDos attack - or denial of service - has been blamed for the outage, with pages currently available intermittently.
A DDos attack is where multiple compromised systems - often infected with a Trojan virus - are used to target a single system causing a Denial of Service (DoS).
A similar attack affected the NHS a few years ago.
Wikipedia's main account tweeted: "Wikipedia has been experiencing intermittent outages today as a result of a malicious attack.
"We're continuing to work on restoring access. #wikipediadown"
It comes on the same day as Xbox Live went down, although it is unknown if they are linked.
Social media was quick to voice their concerns with one twitter user writing: "I cannot get my dose of random info due to Wikipedia being down."
Another said: "Omg, @Wikipedia is down, and I am not sure how I will fall asleep.
"Wikipedia rabbit holes are my favorite bedtime pastime. It helps me to know bits and pieces of random stuff, and then I can pretend to be smart. Kinda lost without you dear Wiki."
Xbox also experienced server outage problem as gamers complained of a sign-in problem.
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