Yahoo 2013 Data Breach: All 3 Billion Accounts Compromised

The Yahoo breach of 2013 remains the largest data breach in history by number of records. State-sponsored attackers accessed Yahoo user database containing names, email addresses, phone numbers, dates of birth, hashed passwords using the weak MD5 algorithm, and unencrypted security questions and answers. The breach was not discovered for three years.

The breach at Yahoo exposed 3 billion records through state-sponsored attack using forged cookies and stolen backup database. All 3 billion Yahoo accounts worldwide — the largest data breach in history The incident highlights the ongoing challenges organizations face in protecting sensitive user data against increasingly sophisticated attack vectors. Security researchers have noted that breaches of this magnitude often result from a combination of technical vulnerabilities and organizational failures in security practices.

Current status: Yahoo settled class action for $117.5 million; Verizon acquired Yahoo at $350 million discount. Affected users should take immediate steps to protect their accounts, including changing passwords, enabling multi-factor authentication, and monitoring financial accounts for unauthorized activity. Filing a DSAR with Yahoo can help you understand what data was exposed and request its deletion.