PII (personally identifiable information) is information that identifies a person directly or can do so when combined with other data. Direct identifiers include names, government identification numbers, passport details, and email addresses; indirect identifiers can include birth dates, precise location, or unique account attributes. The term is used broadly in security, but its legal scope varies: laws and regulations may use different definitions, such as “personal data” under the GDPR or protected health information under HIPAA.
PII is a high-value target because unauthorized access or disclosure can enable identity fraud, targeted phishing, or privacy harm. It may be exposed through compromised applications, cloud storage, logs, endpoints, or third parties. Practitioners should inventory and classify it, collect and retain only what is needed, restrict access, and protect it with encryption or tokenization where appropriate. Monitoring and tested procedures for investigating exposure are important, while retention, deletion, and notification duties depend on the applicable jurisdiction and sector.