The cause of the breach was not immediately clear, but the unusual scope of the problem suggested that it was not limited to a single account or service. While account compromises are not unusual, experts were surprised at the sheer scale and coordination of the Wednesday's incident.
"This appears to be the worst hack of a major social media platform yet," said Dmitri Alperovitch, who co-founded cybersecurity company CrowdStrike.
Twitter said it was investigating what it called a "security incident" and would be issuing a statement shortly. Shares in the social media company tumbled almost 5 percent in trading after the market close before paring their losses.
Some of the tweets were swiftly deleted but there appeared to be a struggle to regain control of several of the accounts. In the case of billionaire Tesla Chief Executive Elon Musk, for example, one tweet soliciting cryptocurrency was removed and, sometime later, another one appeared, and then a third.
Among the others affected: Amazon founder Jeff Bezos, investor Warren Buffett, Microsoft co-founder Bill Gates, and the corporate accounts for Uber and Apple. Several accounts of cryptocurrency-focused organizations were also hijacked.
Biden's campaign was "in touch" with Twitter, according to a person familiar with the matter. The person said the company had locked down the Democrat's account "immediately following the breach and removed the related tweet." Tesla and other affected companies were not immediately available for comment.
Publicly available blockchain records show that the apparent scammers have already received more than $100,000 worth of cryptocurrency.
Alperovitch, who now chairs the Silverado Policy Accelerator, said that, in a way, the public had dodged a bullet so far.
"We are lucky that given the power of sending out tweets from the accounts of many famous people, the only thing that the hackers have done is scammed about $110,000 in bitcoins from about 300 people," he said.