Personally identifiable information, or PII, is any data that can be used to identify a specific person. Common examples include names, email addresses, phone numbers, home addresses, government ID numbers, dates of birth, and account details. Some data is directly identifying on its own, while other fields become identifying when combined with additional records.
PII matters in cyber security because it creates privacy, fraud, and extortion risk. Attackers seek it to steal identities, open fraudulent accounts, impersonate employees, or build convincing phishing and social-engineering lures. In breach investigations, defenders treat PII as sensitive content that requires fast scoping, access-log review, containment, and notification decisions. Protecting PII usually involves data minimization, encryption, strict access controls, and monitoring for unusual downloads or exfiltration.