It is not clear if the hacker posted anything on Mr Obama's Twitter page
President Barack Obama talks on the phone en route to George Mason University in Fairfax, Virginia, in this handout picture taken on March 19, 2010
A Frenchman who police say hacked Twitter accounts belonging to US President Barack Obama and celebrities could face jail.
The unemployed 25-year-old was arrested on Tuesday after an operation lasting several months, conducted by French police with agents from the FBI.
The 25-year-old is said to have hacked into the micro-blogging website, by simply guessing users' passwords.
The suspect reportedly targeted other celebrities, including Britney Spears.
After being questioned by police, he was ordered to appear at court in the central French city of Clermont-Ferrand on 24 June.
Hacking into a database in France is a crime which can carry a two-year jail term.
The suspect, who used the pseudonym "Hacker Croll", had no specialist training, Adeline Champagnat, head of the French central office against online fraud, told Reuters news agency.
He gained access to Twitter accounts by simply working out the answers to password reminder questions on targets' e-mail accounts, according to investigators.
An unemployed Frenchman has been arrested for targeting the Twitter accounts of President Barack Obama and singer Britney Spears, French police said on Wednesday.
Captain Adeline Champagnat, a senior member of the police cyber crimes unit, said the 25-year-old man gained access to passwords of Twitter administrators and used them to try to break into the accounts of U.S. politicians and stars.
"He didn't get as far as their personal accounts. But he had gained control of Twitter," she told Reuters Television in an interview.
She said the FBI had tipped off the French police in July last year that one or more people were trying to get access to Twitter and had gained control of the social network.
That enabled them to create and delete accounts and steal confidential information.
The hacker, who went by the online name of HackerCroll, is under arrest in the central French town of Clermont Ferrand.
He was known to have carried out minor internet fraud but in this case was driven by the thrill of the challenge and appeared to be more interested in the private life of his victims than on obtaining sensitive data, Champagnat said.
"His aim wasn't to make money. It was simply to show that he was able to access accounts of Twitter members. And the best proof of that is that he did screen grabs of certain confidential data which he tried to post on blogs that are reserved for pirates or hackers," she said.
She said several FBI agents were currently in France to help their French counterparts carry out searches.
"The collaboration was very good with the FBI and it's always very good with the FBI, because there's a real exchange of information. It's good cooperation to arrest the offender," she said.
P Diddy posted this picture of himself with his wax model (Right) on his Twitter page. He has 2.3m followers.Pete Cashmore (middle) topped the most influential on Twitter poll but TV presenter and comedian Stephen Fry (left) is far more well-known
Twitter is probably best known for its celebrity users who discuss their lives down to the most trivial detail.
So it is quite a surprise that the most influential Briton on the social networking site is a virtual unknown.
Pete Cashmore, 24, is a Scottish internet entrepreneur and social media guru, who has 1.8million followers on the site.
He beat Stephen Fry into second place, even though the comedian is credited with sending Twitter's profile soaring with his updates and banter with celebrity friends. Fry even used it to send out messages when he was trapped in a lift earlier this year.
Cashmore is chief executive of Mashable, one of the biggest technology blogs.
He founded the firm in 2005 from his bedroom in his parents' home in Banchory, near Aberdeen, and now oversees a business with revenues of seven-figures with offices all over the world.
On Twitter he uses his 'tweets' - 140-character updates - to break the latest stories from his blog and discuss them. Recent messages have been on McDonald's adding free wi-fi to its stores, Google Earth installed in Audi cars and his top ten digital gifts for Christmas.
He has proved popular with the public because his tweets discuss technological changes in terms of everyday life issues, such as shopping, music and social networking.
The list of the most influential Britons on Twitter was compiled by mobile phone maker INQ.
It calculated an 'influence rating' for each 'tweeter' by measuring how many followers they had, the rate and number of tweets, how many times their posts were linked to by other users and how many times other users mentioned them.
Scottish tennis star Andy Murray, in 11th place, was the most influential sportsman.
Sarah Brown, the Prime Minister's wife, at number 14, was the most influential British political figure, followed by London mayor Boris Johnson at 18.
Mrs Brown has one million followers while the official Labour Party's account only has 8,200.
Iranian hackers brought down micro-blogging website Twitter for around two hours this morning.
The attack took place at around 6am and left the site's estimated 30million users unable to send messages or post 'tweets'.
The main Twitter homepage had been replaced with a black and red screen featuring an image of a green flag.
The page carried the message: 'This site has been hacked by the Iranian Cyber Army.
The site reappeared around two hours later, with staff telling users: 'We are working to recovery from an unplanned downtime and will update more as we learn the cause of this outage.'
It is believed that Twitter's DNS records were hijacked in the attack meaning that users who were trying to visit the site were actually redirected to the new page.
The DNS, which stands for Domain Name System, connects the name of a website, in this case twitter.com, to the servers which hold its contents.
A short statement was issued on the company's blog. The site reappeared around two hours later, with staff telling users: 'We are working to recovery from an unplanned downtime and will update more as we learn the cause of this outage.'
It is believed that Twitter's DNS records were hijacked in the attack meaning that users who were trying to visit the site were actually redirected to the new page.
The DNS, which stands for Domain Name System, connects the name of a website, in this case twitter.com, to the servers which hold its contents.
A short statement was issued on the company's blog.
-In a clear and simple way, this Cisco graphic shows the relationship of the parties in a DDOS attack. -
At 9 a.m., millions of users of Twitter.com found themselves unable to access the microblogging Web site, the modern version of the telephone party line through which more than 40 million people announce what they are doing, reading, eating and thinking at any given moment.
Undaunted, the rejected Twitterers trooped to Facebook.com, the social networking site that has more than 200 million users, which has "status updates" that mimic Twitter feeds. But before users could begin to type, "Is sad that Twitter is down," a terrible and panic-inducing discovery: Facebook was down, too.
Kathleen Loughlin, a spokeswoman for Facebook, also cited a denial-of-service attack, which she said "resulted in degraded service for some users." She added that no user data were at risk during the attack and promised that Facebook was "continuing to monitor the situation to ensure that users have the fast and reliable experience they've come to expect from Facebook."
"On this otherwise happy Thursday morning, Twitter is the target of a denial-of-service attack," Twitter co-founder Biz Stone wrote on the official Twitter blog. "Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as . . . Twitter for intended customers or users. We are defending against this attack now."
The first big DDoS attack, in February 2000 took down some of the Web's most popular sites for hours, including Yahoo, CNN, eBay, Amazon.com, Buy.com, and E*Trade. The U.S. Federal Bureau of Investigation promptly held a news conference to discuss the disruption to the Internet and eventually tracked down the perpetrator, 15-year-old "Mafiaboy," after he bragged about it to friends online.
Mafiaboy was most likely trying to get attention, like script kiddie hackers do when they deface Web sites. Other attackers have different agendas. For instance, there are politically motivated DDoS attacks, such as those involving Russian and Georgian sites last year. Estonia sites were attacked in 2007. Meanwhile, the origin of recent DDoS attacks targeting U.S. government sites and sites in South Korea remain a mystery.
---------
Twitter users were unable to log in for several hours after the social networking site became the victim of a cyber attack.
-----
What's a denial-of-service attack? A denial-of-service (DoS) attack is any effort designed to interfere with access to a Web site or Internet service. A common method of attack involves flooding a target server with so many communications requests that legitimate traffic can not get through. This can shut down or slow down the site temporarily.
Web sites aren't the only things that can be targeted in DoS attacks. Unplugging someone's computer is a very basic type of DoS attack.
What's a distributed-denial-of-service (DDoS) attack? Because Web sites are built to handle a lot of traffic, it can take millions of simultaneous communications requests to have enough affect on the performance of the server for an attack. In a DDoS attack, tens of thousands or even millions of computers are used to send traffic to the target site all at the same time and repeatedly."It's a bit like 15 fat men trying to get through a revolving door at the same time--nothing can move."
What's a botnet? The hijacked PCs that are used in a DDoS attack comprise a botnet. The individual computers are called "bots," "zombies" or "slaves" and are controlled remotely by the "master" attacker. The attacker relays instructions to the bots via a command-and-control server, typically using IRC (Internet Relay Chat). Botnets are also used to distribute spam. Some newer botnets, like one created by a version of Conficker, relay instructions via peer-to-peer.
How many bots are needed to take down a Web site? The number depends on how much resources, servers and bandwidth, the target site has. It can take 25,000 to 50,000 bots to cripple a typical site and as few as 10,000 or less for a small Web site, according to Kevin Stevens, a security researcher for SecureWorks' Counter Threat Unit.
It's difficult to know exactly how big any particular botnet is and guesses vary widely. For example, estimates of the Conficker botnet ranged from 500,000 PCs to 10 million.
What kind of damage can a DoS attack do? A DoS can make a Web site completely inaccessible to anyone for a period of time, like the most recent attack did with Twitter. Or it can be equivalent to a hiccup, slowing down page loads or affecting only part of the site.
Sites that aren't in the direct line of fire can also be affected. For example, if a company that is attacked is hosting images or content that is fed to other sites, those other sites may have trouble. So many sites feature Twitter updates that it's likely some of those associated sites were impacted when Twitter was down and the ancillary site's requests to get updates were ignored.
How can a DDoS be prevented or stopped?
In 2001, the White House was able to thwart a DDoS attack that was programmed into the code of the Code Red virus by moving the site away from the targeted IP address.
And in 2005, Microsoft sidestepped a DDoS that was going to be triggered by PCs infected with the Blaster virus by killing the targeted IP address.
A company can reduce its risk by buying plenty of servers and bandwidth, and hosting content on backup servers. Companies can also limit the number of connections that the Web server allows at any one time and set the firewall to block certain types of data that are used in DDoS attacks, said SecureWorks' Stevens.
What can individuals do to prevent their computers from being used in a DDoS attack?
To keep malware off a computer, people should install the latest operating system and application patches, update their antivirus and other security software, consider using auto-updates for browsers and be careful about opening up attachments and visiting Web sites.
