The internet around the world is being slowed down in what security experts are describing as the "biggest cyber-attack in history".
It was caused by a row between the anti-spam NGO Spamhaus and the web-hosting service Cyberbunker.
Spamhaus claims that Cyberbunker and "criminal gangs" from Eastern Europe and Russia are behind the attack.
It is having an impact on multimedia services like Spotify and Netflix, and experts worry it could escalate to affect banking and email services.
Five Cyber-police forces around the world are investigating the attacks.