Yahoo has disclosed a massive security breach that may be the largest ever — much larger than a 500 million-account breach that came to light back in September, which was thought at the time to be the largest on record, USA Today reports.
The breach disclosed today took place in August 2013 and “may have resulted in the theft of data associated with more than one billion user accounts,” the story reports.
Yahoo shares reportedly fell 2% in after-hours trading.
“The new revelation comes at a time when cybercrime issues loom large as never before,” USA Today notes. “The CIA has accused Russia of specifically attempting to tamper with the U.S. election via hacked emails, ransomware hit the nation’s seventh-largest transit system, in San Francisco, and a monster botnet of hijacked devices took down much of the East Coast’s Internet traffic for a day in October.”
Yahoo said it does not know who was behind the breach announced today, but indicated it does not believe it is linked to the September breach.