The Yahoo breach could have affected more accounts than previously reported.

Yahoo confirmed last week that data from at least 500 million user accounts had been stolen in the company's network from late 2014.

However, the number of affected accounts may be between 1 billion and 3 billion, Business Insider reported Friday, citing one former Yahoo executive who is familiar with the company's security and still speaks to employees at the company.

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The hack could be much larger than Yahoo has said due to how the company stores information on and authenticates users. All of Yahoo's products were affected by the breach and are tied to one user database, the unnamed source said.

That central database is what got compromised, and therefore, this executive believes that the scale is much larger than Yahoo reported.

It is important to note that Business Insider only cited one former executive, and it is unclear his or her motivations.

Yahoo declined to share specifics on how its network architecture works in a request from Mashable.

Yahoo had an estimated 700 million to 1 billion monthly active users in 2014, at the time of the hack. That number does not include inactive accounts.

Even though the hacker may have had access to more user data, there's a chance it was not all breached.

A Yahoo spokesperson declined to comment on the report and noted that this is an ongoing investigation to Mashable.

"Based on the ongoing investigation, Yahoo believes that information associated with at least 500 million user accounts was stolen and the investigation has found no evidence that the state-sponsored actor is currently in Yahoo's network," Yahoo wrote in its press release last week.

Already, the hack is believed to be one of the biggest in history.

Verizon is still in the midst of an acquisition of Yahoo's core business for $4.83 billion.