A squabble between a group fighting spam and a Dutch company that hosts websites said to be sending spam has escalated into one of the largest computer attacks on theinternet, causing widespread congestion and jamming crucial infrastructure.
Millions of ordinary internet users have experienced delays in services like Netflix or could not reach a particular website for a short time.
However, for the internet engineers who run the global network the problem is more worrisome. The attacks are becoming increasingly powerful, and computer security experts worry that if they continue to escalate people may not be able to reach basic internet services, like email and online banking.
The dispute started when the Geneva-based spam-fighting group Spamhaus added the Dutch company Cyberbunker to its blacklist, which is used by email providers to weed out spam.
Cyberbunker, named for its headquarters, a five-story former Nato military bunker near a Dutch town called Goes, offers hosting services to any website "except child porn and anything related to terrorism," according to its website.
A spokesman for Spamhaus, which is based in Europe, said the attacks began March 19th but had not stopped the group from distributing its blacklist.
Patrick Gilmore, chief architect at Akamai Networks, a digital content provider, said Spamhaus' role was to generate a list of spammers.
Mr Gilmore said the attacks, which are generated by swarms of computers called botnets, concentrate data streams that are larger than the internet connections of entire countries. He likened the technique, which uses a long-known flaw in the internet's basic plumbing, to using a machine gun to spray an entire crowd when the intent is to kill one person.
The attacks were first mentioned publicly last week by Cloudflare, an internet security firm in Silicon Valley that was trying to defend against the attacks and as a result became a target.
"These things are essentially like nuclear bombs," said Matthew Prince, chief executive of Cloudflare. "It's so easy to cause so much damage."
The so-called denial of service, or DDoS, attacks have reached previously unknown magnitudes, growing to a data stream of 300 billion bits per second. "It is a real number," Mr Gilmore said. "It is the largest publicly announced DDoS attack in the history of the internet."
Spamhaus, one of the most prominent groups tracking spammers on the Internet, uses volunteers to identify spammers and has been described as an online vigilante group. In the past, blacklisted sites have retaliated against Spamhaus with denial-of-service attacks, in which they flood Spamhaus with traffic requests from personal computers until it falls offline. But in recent weeks, the attackers hit back with a far more powerful strike that exploited the internet's core infrastructure, called the Domain Name System, or DNS.
That system functions like a telephone switchboard for the internet. It translates the names of websites like Facebook. com or Google. com into a string of numbers that the web's underlying technology can understand. Millions of computer servers around the world perform the actual translation.
In the latest incident, attackers sent messages, masquerading as ones coming from Spamhaus, to those machines, which were then amplified drastically by the servers, causing torrents of data to be aimed back at the Spamhaus computers. 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.
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, computer security experts say, because those servers cannot be shut off without halting the internet.
Cyberbunker brags on its website that it has been a frequent target of law enforcement because of its "many controversial customers." The company claims that at one point it fended off a Dutch SWAT team. "Dutch authorities and the police have made several attempts to enter the bunker by force," the site said. "None of these attempts were successful."