An intriguing and puzzling series of events took place on Twitter (TWTR  ) on Wednesday, with dozens of accounts belonging to significant personalities and brands being simultaneously hacked as part of an extensive cryptocurrency scam. While the issue seems to be under control now, the identity of the hacker remains unknown.

The hacking campaign targeted accounts belonging to major twitter users, including politicians and celebrities. Among the individuals targeted were Bill Gates, Joe Biden, Elon Musk, former President Barack Obama, Mike Bloomberg, and Jeff Bezos. A few major brands were also targeted, including Apple (AAPL  ), Uber (UBER  ), Square (SQ  ), and Cash App.

The scam itself revolves around cryptocurrency. The scam posts made to Twitter attempted to trick users into sending bitcoin to the scammer with the promise of double being sent back. Unfortunately, it would appear that some Twitter users had indeed fallen for the scam, with some $100,000 in bitcoin being believed to have been sent to scammers. The ID of the bitcoin wallet used in some of the posts was posted to Twitter, allowing users to view transactions that had taken place.

According to The Verge, the hacking campaign began at around 4 p.m. ET when Elon Musk's account was used to post the first scam link. Perhaps not coincidentally, as Elon Musk's Twitter account has been the subject of various cryptocurrency scams in the past. In the hours after Musk's post, other accounts began to post similar links, each with a message unique to the hacked user. Musk's hacked post read, "I'm feeling generous because of Covid-19", while Joe Biden's read "I am giving back to the community" and Bill Gates' read "Everyone is asking me to give back, and now is the time."

Twitter became aware of the situation just before 6 p.m. ET and began looking into the hacking.

"Once we became aware of the incident, we immediately locked down the affected accounts and removed Tweets posted by the attackers. We have locked accounts that were compromised and will restore access to the original account owner only when we are certain we can do so securely." said Twitter.

The company went about removing posts, though, as it did some users reported being unable to post, and some were getting error messages. Late into the evening, Twitter finally appeared to have the situation under control. According to the company, an internal admin tool was used to gain access to administrative privileges and bypass Twitter's security measures.

The hacking took place after markets closed, but the hacks were enough to drive Twitter's stock price down in after-market trading. Twitter's shares were down 4% from Wednesday's closing price when the markets opened on Thursday. Twitter's price was still below Wednesday's closing price at noon. Twitter's inability to recover its share price might not be entirely because of the hacks, however, as the Dow Jones Industrial Average (DIA  ) and Nasdaq Composite (QQQ  ) were both down during the day as well.