The internet around the world has been slowed down in what security experts are describing as the biggest cyber-attack of its kind in history.
A row between a spam-fighting group and hosting firm has sparked retaliation attacks affecting the wider internet.
The BBC reports it is having an impact on popular services like Netflix and experts worry it could escalate.
Non-profit organisation Spamhaus, a group that aims to help email providers filter out spam, recently blocked servers maintained by Dutch web host Cyberbunker, which states it will host anything with the exception of child pornography or terrorism-related material.
Spamhaus has alleged that Cyberbunker, in cooperation with "criminal gangs" from Eastern Europe and Russia, is behind the attack.
Steve Linford, chief executive for Spamhaus, told the BBC the scale of the attack was unprecedented.
Mr Linford said the attacks were peaking at 300 gigabits per second. "Normally when there are attacks against major banks, we're talking about 50 gb/s."
The attackers have used a tactic known as Distributed Denial of Service (DDoS), which floods the intended target with large amounts of traffic in an attempt to render it unreachable.
Spamhaus is able to cope, the group says, as it has highly distributed infrastructure in a number of countries.
Mr Linford told the BBC that the attack was being investigated by five different national cyber-police-forces around the world.
He claimed he was unable to disclose more details because the forces were concerned that they too may suffer attacks on their own infrastructure.
Sven Olaf Kamphuis, who claims to be a spokesman for Cyberbunker, said, in a message, that Spamhaus was abusing its position, and should not be allowed to decide "what goes and does not go on the internet".
The knock-on effect is hurting internet services globally, said Prof Alan Woodward, a cybersecurity expert at the University of Surrey.
Spamhaus is supported by many of the world's largest internet companies who rely on it to filter unwanted material.