Twitter, once derided as a frivolous way to tell friends of what you are eating and when you're going to bed, has grown up -- the hard way.
The cyber-attack that paralyzed the social networking service Thursday signaled that Twitter had become big enough to attract the attention of malicious Internet hackers, who may have been motivated by profit.
No one knows for sure who was behind the "denial of service" strike that crippled the website for hours, and which was also aimed at popular Internet properties Facebook, Google and possibly YouTube.
Speculation as to the perpetrators ran from bored teenagers to cyberspace fighting between Russian and Georgian political operatives.
Several security experts said they saw the fingerprints of a sophisticated operation involving "botnets" -- giant armies of personal computers that have been silently taken over by hackers, unbeknown to their owners.
"Botnets are a very stable platform to engage in all sorts of cyber crime," said Thomas Holt, a professor at Michigan State's School of Criminal Justice. For some hackers, using "Twitter as a target is a good way of measuring" the power of their botnet.
By showcasing its disruptive effect, hackers can use the attack as a calling card for their services for anyone who wants to derail a rival or use the network to send huge volumes of unwanted e-mail.
Jerry Dixon, former director of the National Cybersecurity Division at the Department of Homeland Security, said the perpetrators could be a group of hackers trying to show that they're capable of taking down a hugely popular social network.
"They are saying, 'Look what I'm capable of doing,' " Dixon said. "It's someone trying to make a name for themselves."
That could be for bragging rights or a more nefarious purpose. The hackers who crippled a service as prominent as Twitter could conceivably sell their skills.
"They would be like hit men, but with digital packets instead of bullets," said Dixon, now a security analyst with the nonprofit group Team Cymru.
Indeed, there have been instances of hackers being paid to take down sites.
In 2004, satellite TV retailer Saad Echouafni was indicted in federal court in Los Angeles on suspicion of paying to attack three online competitors. One of the hackers pleaded guilty, but Echouafni fled and is at large, according to the FBI.
