Two of the largest social media sites, Twitter and Facebook, fell to their knees early Thursday morning, with both being severely disrupted by a coordinated attack.

Whenever any of the 45 million users belonging to the Twitter community tried to access the site yesterday they were presented with the “fail whale”, a timeout because the servers took too long to respond or simply nothing at all. On the other hand, a portion of the 250 million Facebook users experienced degraded performance, including delays with logging in to the site or posting items. This no doubt left many people frustrated, with these social networking sites now being an integral part of people’s lives.

Both companies have teamed up with Google to investigate the attack. In a statement yesterday, Google said, “We are aware that a handful of non-Google sites were impacted by a DOS attack this morning, and are in contact with some affected companies to help investigate this attack.”

So how did the attack take place?

The attack stemmed from a botnet, where thousands of infected “zombie” computers that are controlled by the attacker simultaneously submit data to the sites with the aim of overloading the servers and making them inaccessible. This type of attack is commonly called a distributed denial-of-service attack, and is notoriously hard (and expensive) to defend against. Such an incident highlights the vulnerability that these fast-growing social media sites face and puts the spotlight on how they can be an easy target because of their popularity. The motive for the attack is unknown, but some people are mulling over the idea that it could have been targeted to one person who has a presence on these sites (a pro-Georgian blogger known as Cyxymu). If this is the case, then someone really wanted to silence this guy and send out a message. Twitter itself refuses to be drawn into the debate, stating on their blog, “As to the motivation behind this event, we prefer not to speculate.”

This attack is just another feather in these cyber criminals’ hat and makes me wonder, who’s next? For now, we’ll let the investigation team do their job and see how the news unfolds over the next few weeks.

Whatever the outcome, one thing’s for sure… Twitter was far less equipped to cope with such an attack than Facebook. Wouldn’t you just love to be a fly on the wall in Twitter’s next meeting with their hosting providers?