Media playback is unsupported on your device Media caption The BBC's Rory Cellan-Jones explains why the attack is like a "motorway jam", alongside expert David Emm from Kaspersky Lab 
 
 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. 
 
 Experts worry that the row could escalate to affect banking and email systems. 
 
 Five national cyber-police-forces are investigating the attacks. 
 
 Spamhaus, a group based in both London and Geneva, is a non-profit organisation that aims to help email providers filter out spam and other unwanted content. 
 
 To do this, the group maintains a number of blocklists - a database of servers known to be being used for malicious purposes. 
 
 Recently, Spamhaus blocked servers maintained by Cyberbunker, a Dutch web host that states it will host anything with the exception of child pornography or terrorism-related material. 
 
 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". 
 
 Spamhaus has alleged that Cyberbunker, in cooperation with "criminal gangs" from Eastern Europe and Russia, is behind the attack. 
 
 Cyberbunker has not responded to the BBC's request for comment. 
 
 'Immense job' 
 
 Steve Linford, chief executive for Spamhaus, told the BBC the scale of the attack was unprecedented. 
 
 "We've been under this cyber-attack for well over a week. 
 
 'Decapitating the internet' Image caption The DNS ensures that you are sent to the correct site when you enter a web address Writing exactly one year ago for the BBC, Prof Alan Woodward predicted the inherent weaknesses in the web's domain name system. He wrote: "It is essentially the phone book for the internet. If you could prevent access to the phone book then you would effectively render the web useless." Read Prof Woodward's full article 
 
 "But we're up - they haven't been able to knock us down. Our engineers are doing an immense job in keeping it up - this sort of attack would take down pretty much anything else." 
 
 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. 
 
 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. 
 
 In this case, Spamhaus's Domain Name System (DNS) servers were targeted - the infrastructure that joins domain names, such as bbc.co.uk, the website's numerical internet protocol address. 
 
 Mr Linford said the attack's power would be strong enough to take down government internet infrastructure. 
 
 "If you aimed this at Downing Street they would be down instantly," he said. "They would be completely off the internet." 
 
 He added: "These attacks are peaking at 300 Gbps (gigabits per second). 
 
 "Normally when there are attacks against major banks, we're talking about 50 Gbps" 
 
 Clogged-up motorway 
 
 The knock-on effect is hurting internet services globally, said Prof Alan Woodward, a cybersecurity expert at the University of Surrey. 
 
 "If you imagine it as a motorway, attacks try and put enough traffic on there to clog up the on and off ramps," he told the BBC. 
 
 "With this attack, there's so much traffic it's clogging up the motorway itself." 
 
 Arbor Networks, a firm which specialises in protecting against DDoS attacks, also said it was the biggest such attack they had seen. 
 
 "The largest DDoS attack that we have witnessed prior to this was in 2010, which was 100 Gbps. Obviously the jump from 100 to 300 is pretty massive," said Dan Holden, the company's director of security research. 
 
 "There's certainly possibility for some collateral damage to other services along the way, depending on what that infrastructure looks like." 
 
 Spamhaus said it was able to cope as it has highly distributed infrastructure in a number of countries. 
 
 The group is supported by many of the world's largest internet companies who rely on it to filter unwanted material. 
 
 Mr Linford told the BBC that several companies, such as Google, had made their resources available to help "absorb all of this traffic". 
 
 The attacks typically happened in intermittent bursts of high activity. 
 
 "They are targeting every part of the internet infrastructure that they feel can be brought down," Mr Linford said. 
 
 "Spamhaus has more than 80 servers around the world. We've built the biggest DNS server around." ||||| When Spamhaus requested aid from CloudFlare, the attackers began to focus their digital ire on the companies that provide data connections for both Spamhaus and CloudFlare. 
 
 Questioned about the attacks, Sven Olaf Kamphuis, an Internet activist who said he was a spokesman for the attackers, said in an online message that, “We are aware that this is one of the largest DDoS attacks the world had publicly seen.” Mr. Kamphuis said Cyberbunker was retaliating against Spamhaus for “abusing their influence.” 
 
 “Nobody ever deputized Spamhaus to determine what goes and does not go on the Internet,” Mr. Kamphuis said. “They worked themselves into that position by pretending to fight spam.” 
 
 A typical denial-of-service attack tends to affect only a small number of networks. But in the case of a Domain Name System flood attack, data packets are aimed at the victim from servers all over the world. Such attacks cannot easily be stopped, experts say, because those servers cannot be shut off without halting the Internet. 
 
 “The No. 1 rule of the Internet is that it has to work,” said Dan Kaminsky, a security researcher who years ago pointed out the inherent vulnerabilities of the Domain Name System. “You can’t stop a DNS flood by shutting down those servers because those machines have to be open and public by default. The only way to deal with this problem is to find the people doing it and arrest them.” 
 
 The heart of the problem, according to several Internet engineers, is that many large Internet service providers have not set up their networks to make sure that traffic leaving their networks is actually coming from their own users. The potential security flaw has long been known by Internet security specialists, but it has only recently been exploited in a way that threatens the Internet infrastructure. 
 
 An engineer at one of the largest Internet communications firms said the attacks in recent days have been as many as five times larger than what was seen recently in attacks against major American banks. He said the attacks were not large enough to saturate the company’s largest routers, but they had overwhelmed important equipment.
– If the Internet seems a little slow to you lately, that's because it's in the midst of what is being called the biggest cyberattack of all time, reports the BBC. The fight is between a spam-fighting group, Spamhaus, and a web-hosting company, Cyberbunker, but it has grown to the point that it's affecting the entire Internet and its infrastructure. Millions of users are experiencing delays while trying to reach websites or while using services like Netflix, and experts fear that if the attacks continue to grow in power, people may not be able to access things like email or online banking. It all started when Spamhaus, which publishes a blacklist that email providers use to weed out spam, put Cyberbunker on its list of spammers. Cyberbunker retaliated, but its attack on Spamhaus ended up having a much larger impact. One architect at a digital content provider likened it to, as the New York Times puts it, using a machine gun in an effort to assassinate one person. The distributed denial of service (DDoS) attacks "are essentially like nuclear bombs" that exploit the Internet's Domain Name System (DNS), says an exec at a group that tried to defend against the attacks and ended up becoming a target. "It's so easy to cause so much damage." And, notes the architect, this is "the largest publicly announced DDoS attack in the history of the Internet." Cyberbunker says Spamhaus is a vigilante group "abusing [its] influence," but the architect notes that Cyberbunker is "just mad" that it got caught spamming. One security researcher says the only way to stop the attack is to arrest the people responsible. Five cyber-police forces around the globe are investigating.