On the site's corporate blog, Twitter co-founder Biz Stone said: "On this otherwise happy Thursday morning, Twitter is the target of a denial of service attack. Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as online banks, credit card payment gateways, and in this case, Twitter for intended customers or users.
"We are defending against this attack now and will continue to update our status blog as we continue to defend and later investigate."
Jerry A. DiColo of Dow Jones Newswire describes this type of attack for non-geeks such as me:
Denial-of-service attacks are a common weapon employed by cyber criminals to disrupt the working of Web sites. Perpetrators enlist millions of computers to attempt to access a particular site. The site cannot handle the massive increase in traffic, and is rendered inaccessible.
While disruptive and hard to trace, this type of cyber attack is considered by experts to be a relatively unsophisticated technique. The attack itself doesn't attempt to infiltrate the internal operations of a company's computer infrastructure. It simply renders its Web site inactive.
Barret Lyons writes on bylon.com how it could be a DDoS attack:
At a presentation I gave at an International Terrorism and Intelligence conference, I discussed how Twitter is an obvious DDoS target. Well about 30 days later they’re in the thick of it.
Twitter is down and their network has clear signs of massive failure. In the several hundred (if not more) cases of DDoS I have had experience with, this looks like a very clear case of an attack.
Congestion is a very clear sign of a DDoS attack. In this case you will see on a traceroute clean hops up to the last few, where the network starts to get congested. Basically that means each step of the network is clean until things concentrate at the end.
The assumption is the congestion is caused by DDoS and not a system administrator creating a routing loop or something whacky like that.
They also only appear to have ONE network provider (NTT), which is rather insane these days. It also makes targeting Twitter a much less complicated task.
Using very basic tools it is possible to see that the congestion on their network is rather extreme. It’s possible to deduce that the congestion is probably due to a DDoS attack.
There have been reports that Facebook and Live Journal are having trouble as well. But my Facebook page is alive a well for the moment.