UPDATE 6-Hacker attacks silence Twitter, slow Facebook
* Twitter site has service outage
* Company attributes outage to denial-of-service attack
* Some Facebook users have trouble logging in (Adds detail about Georgian blogger)
SAN FRANCISCO, Aug 6 (Reuters) - Twitter and Facebook suffered service problems from hacker attacks on Thursday, raising speculation about a coordinated campaign against the world's most popular online social networks.
The attacks, which came a month after the White House website was targeted in a similar online assault, left millions unable to carry out daily routines that have assumed an increasingly central part of their lives.
The incidents also underscored the vulnerability of fast-growing Internet social networking sites that have been heralded as powerful new political tools to counter censorship and authoritarianism.
Twitter, which allows people to broadcast short, 140-character text messages over the Internet, became a key form of communication in Iran amid the protests and clampdown that followed the country's disputed June elections.
A Facebook executive said Thursday's cyber attacks were aimed at a Georgian blogger with accounts at the various affected sites, according to a report on technology news site CNET.
In a blog post earlier on Thursday, Twitter co-founder Biz Stone said the company preferred not to speculate about the motivation of the malicious attack that knocked the site offline and made it inaccessible for several hours earlier in the day.
"Twitter has been working closely with other companies and services affected by what appears to be a single, massively coordinated attack," said Stone.
Members of Facebook, the world's largest Internet social network with more than 250 million active users, saw delays logging in and posting to their online profiles. Like Twitter, Facebook said the problems appeared to stem from a so-called denial of service attack, a technique in which hackers overwhelm a website's servers with communications requests.
Once access to Twitter had been restored, many of the site's users posted short messages lamenting the disturbance.
"now I know Im addicted to Twitter...I wasnt rite all day," Twitter user hotlilNINA posted.
Speculation swirled on the Internet that other sites, including Google, had also come under attack, after relatively lesser-known site LiveJournal said it, too, had been targeted by hackers on Thursday. But those rumors could not be confirmed.
Google said in an emailed statement that it was in contact with some non-Google sites that were impacted by Thursday's attacks to help investigate. Continued...
