Yahoo said a major security breach in 2013 compromised all 3 billion accounts the company maintained, a threefold increase over the estimate it disclosed previously, Ars Technica reported.

The revelation, contained in an updated page about the 2013 hack, is the result of new information and the forensic analysis of an unnamed security consultant. Previously, Yahoo officials said about 1 billion accounts were compromised. With Yahoo maintaining roughly 3 billion accounts at the time, the 2013 hack would be among the biggest ever reported.

"We recently obtained additional information and, after analyzing it with the assistance of outside forensic experts, we have identified additional user accounts that were affected," Yahoo officials wrote in the update. "Based on an analysis of the information with the assistance of outside forensic experts, Yahoo has determined that all accounts that existed at the time of the August 2013 theft were likely affected."

The information taken in the heist may have included users' names, email addresses, telephone numbers, dates of birth, passwords scrambled using the weak MD5 cryptographic hashing algorithm, and, in some cases, encrypted or unencrypted security questions and answers.