From John Markoff and Nicole Perlroth, New York Times:  A squabble between a group fighting spam and a Dutch company that hosts Web sites said to be sending spam has escalated into one of the largest computer attacks on the Internet , causing widespread congestion and jamming crucial infrastructure around the world.

Millions of ordinary Internet users have experienced delays in services like Netflix or could not reach a particular Web site 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 e-mail and online banking.

The dispute started when the spam-fighting group, called Spamhaus, added the Dutch company Cyberbunker to its blacklist, which is used by e-mail providers to weed out spam. Cyberbunker, named for its headquarters, a five-story former NATO bunker, offers hosting services to any Web site “except child porn and anything related to terrorism,” according to its Web site. . . .

[Chief architect at Akamai Networks Patrick] Gilmore said that 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. . . .

“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 distributed 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. . . .”

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 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.  (graphic:  Steve Gold/Guardian)