Twitter (more info) was down around the world for at least two hours today after being hit by a denial-of-service attack. The problems apparently started around 6am PT this morning and it continues to get longer load times and slowness.Biz Stone (more info) confirms this in Twitter official blog about the DDoS 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.

Twitter has updated their status page about the site is back up, but we are continuing to defend against and recover from this attack.  CNET has also confirmed that Facebook has been slow and ReadWriteWeb talks about LiveJournal briefly unreachable this morning. It has created a lot of buzz in the tech blogs regarding the scaling problems of Twitter. Michael Arrington in his blog comments

These outages are much more serious. 45 million people worldwide now rely on Twitter as a communication platform. If they want to be the “Pulse of the Planet,” it’s time to scale.

Silicon Alley Insider puts it like this

It’s going to be tough to become the next AT&T if you’re dead at 9 a.m. on a Thursday.

Follow-Up

ReadWriteWeb: Twitter, Facebook, and LiveJournal Down at the Same Time! by Sarah Perez

TechCrunch: Serious Twitter Outage Ongoing, Denial of Service Attack by Michael Arrington

VentureBeat: Twitter knocked out by denial of service attack. Facebook, LiveJournal too? by Paul Boutin

Technologizer: Twitter Goes Down, Down, Down by Harry McCracken

Silicon Alley Insider: Twitter Attacked! by Dan Frommer