Yahoo’s 1 billion user accounts hacked Yahoo, already reeling from its September disclosure that 500 million user accounts had been hacked in 2014, disclosed recently that a different attack in 2013 compromised more than 1 billion accounts. The two attacks are the largest known security breaches of one company’s computer network.

It is unclear how many Yahoo users were affected by both attacks. The Internet company has more than 1 billion active users, but it is not clear how many inactive accounts were hacked. Yahoo said it discovered the larger hacking after analysing data files, provided by law enforcement, that an unnamed third party had claimed contained Yahoo information.