Alon Gal, co-founder of Israeli cybersecurity-monitoring firm Hudson Rock has said hackers stole more than 200 million email addresses of Twitter users and posted them on an online hacking forum.
The security researcher in a LinkedIn post on Wednesday said it was “one of the most significant leaks I’ve seen.”
The breach “will unfortunately lead to a lot of hacking, targeted phishing and doxxing,” he said.
Twitter has not commented on the report, which Gal first posted about on social media on Dec. 24, nor responded to inquiries about the breach since that date. It was not clear what action, if any, Twitter has taken to investigate or remediate the issue.
Data on the forum could not be independently verified if they were authentic and came from Twitter.
Screenshots of the hacker forum, where the data appeared on Wednesday, have circulated online, Reuters reports.
Troy Hunt, creator of breach-notification site Have I Been Pwned, viewed the leaked data and said on Twitter that it seemed “pretty much what it’s been described as.”
There were no clues to the identity or location of the hacker or hackers behind the breach. It may have taken place as early as 2021, which was before Elon Musk took over ownership of the company last year.
Claims about the size and scope of the breach initially varied with early accounts in December saying 400 million email addresses and phone numbers were stolen.
A major breach at Twitter may interest regulators on both sides of the Atlantic. The Data Protection Commission in Ireland, where Twitter has its European headquarters, and the U.S. Federal Trade Commission have been monitoring the Elon Musk-owned company for compliance with European data protection rules and a U.S. consent order respectively.
Messages left with the two regulators were not immediately returned on Thursday.