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Cyber attacks forced wildly popular micro-blogging site Twitter offline on Thursday and caused performance problems for hot social-networking service Facebook.
Twitter was down for more than an hour before the
"Twitter is the target of a denial of service attack," Twitter co-founder Biz Stone said in an official company blog.
"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."
Facebook was "degraded" by an early-morning distributed-denial-of-service (DDoS) attack on the Palo Alto, California-based Internet star's website, said Facebook spokeswoman Brandee Barker.
"No user data was at risk and we have restored full access to the site for most users," Barker said.
"We’re continuing to monitor the situation to ensure that users have the fast and reliable experience they’ve come to expect from Facebook."
Twitter and Facebook have reportedly teamed up with Internet powerhouse Google to investigate the attacks.
Hackers evidently employed classic DDoS attacks in which legions of zombie computers, machines infected with viruses, are commanded to simultaneously visit a website.
Such massive onslaught of demand can overwhelm website servers, slowing service or knocking it offline.
"Ten years ago we saw the first DDoS attacks take down some of the world's largest web sites," said Cisco chief security researcher Patrick Peterson.
"The irony here is that botnets, infected criminally-controlled consumer PCs, are the problem. Many of today's tweetless are part of the attack if their PC has been infected due to poor security."
A DDoS attack hit Twitter about 6:00 am local time (1200 GMT) and caused the service to go offline.
"We had a lot of things we'd rather be doing this morning, defending against a DoS wasn't one of them," Stone said in a 'tweet' as the service recovered.
Access to the website continued to be slow, with some aspiring users getting messages telling them that connections had "timed out" because Twitter computers were taking too long to respond.
The attack was the lead topic of conversation at Twitter, as people connected to the service to comment about being unable to connect to the service.
Twitter user Benjamin Hobbs fired off a message saying he "wishes the Denial-of-Service idiots would get a life and leave Twitter alone."
While an everyday chatting tool for many, Twitter has become a weapon used by dissidents to circumvent censorship in places where freedom of speech is suppressed.
Independent information about deadly riots in
Similar to the phenomenon seen a month earlier during Iran's political turmoil, pictures, videos and updates from Urumqi poured onto social networking and image sharing websites such as Twitter, YouTube and Flickr.
In many cases, items were reposted by other Internet users on sites outside
Cyber-sympathizers from around the world joined forces through Twitter in June to help Iranian protestors dodge censorship, get out news of violent clashes and avoid real-world capture following
Cyber attacks on Web pages of Iranian opposition figures have continued in the aftermath of the controversial presidential election.
