Yahoo! Inc (NASDAQ:YHOO) revealed on Wednesday that the login details for as many as one billion accounts may have been hacked in 2013, making it the largest known data breach in history.
The news sent the internet giant’s share price down by 3%, wiping US$1bn from its market value in a matter of hours.
News of this cyber-attack follows closely on from the 500mln accounts implicated in a 2014 breach which Yahoo! only disclosed in September.
The California-based company told users that an “unauthorised party” broke into the accounts in August 2013, claiming that the attack was “state-sponsored”.
The user account information stolen may have included names, email addresses, phone numbers, dates of birth, passwords and other personal information.
Yahoo! is currently being acquired by US telecoms giant Verizon Communications Inc. (NYSE:VZ) for US$4.8bn, but the sale process hasn’t been an easy one.
Verizon said the first hack in September had clearly had a “material impact” on Yahoo!’s value, throwing the deal into a state of confusion.
It remains to be seen how Verizon will react to this latest security scandal and what it could mean, if anything, for the proposed deal.
Shares were down 3% to US$39.50 on Thursday morning.