Personally Identifiable Information (PII): Definition, Risks, and Protection

Key takeaways

• PII is any information that can identify an individual, either alone (direct identifiers) or when combined with other data (quasi-identifiers).
• Sensitive PII (e.g., Social Security numbers, biometric data, medical records) requires stronger protection than nonsensitive PII (e.g., name, ZIP code, gender).
• Big data and online services have increased exposure and regulatory attention; techniques like encryption and anonymization reduce risk.
• Common theft methods include phishing, social engineering, data breaches, and physical document theft.

What is PII?

Personally identifiable information (PII) is any data that can be used to distinguish or trace an individual’s identity, either by itself (direct identifiers) or when linked with other information (quasi-identifiers). Examples of direct identifiers include passport numbers and Social Security numbers; quasi-identifiers include birthdate, ZIP code, and race.

Types of PII

Sensitive PII (examples)
* Social Security number (SSN)
* Financial and credit card information
* Medical and health records
* Passport and driver’s license numbers
* Biometric data (fingerprints, facial recognition)

Nonsensitive (indirect) PII / Quasi-identifiers (examples)
* Full name
* Gender
* ZIP code
* Date and place of birth
* Religion, race

Note: Nonsensitive data alone usually cannot uniquely identify someone, but when combined (de‑anonymization) it can.

Why PII matters in the digital age

Advances in internet services, social media, e‑commerce, and analytics have expanded the collection and linking of PII. Organizations leverage big data to improve services, but aggregated data and poorly protected systems increase the risk of breaches and identity theft. Regulatory frameworks and consumer expectations have grown in response.

Common methods of PII theft

• Phishing emails and malicious websites that trick people into revealing credentials or personal details.
• Social engineering via phone or SMS.
• Data breaches of company databases.
• Physical theft or scavenging of mail and discarded documents.
• Malware, credential stuffing, and exploitation of weak passwords.

Effective strategies to protect PII

For individuals:
* Minimize how much personal information you carry (avoid carrying SSN cards).
* Shred sensitive documents before disposal.
* Use strong, unique passwords and a password manager.
* Enable multi-factor authentication (MFA) where available.
* Keep devices encrypted and locked; use device passwords or biometrics.
* Be cautious about sharing personal details online and verify senders before responding to requests for information.
* When disposing or selling devices, securely wipe or reformat storage.

For organizations:
* Use encryption and access controls for stored and transmitted PII.
* Apply anonymization or pseudonymization when sharing datasets.
* Limit data collection to what is necessary and delete data when no longer needed.
* Implement monitoring, incident response plans, and employee training against phishing and social engineering.
* Conduct regular security assessments and patch management.

Emailing and sharing PII

Email is often insecure. Avoid sending unencrypted PII by email. If you must share PII electronically, use end‑to‑end encryption, secure portals, or verified methods that require recipient authentication.

PII, personal data, and terminology

“Personal data” is a broader term used in some jurisdictions and may include device identifiers, IP addresses, cookies, and behavioral data that are not always considered PII in a narrower sense. Definitions vary by region and law, so classification often depends on context and how data can be linked to an individual.

Regulatory overview (high level)

• United States: PII commonly defined as information that can be used to distinguish or trace an individual’s identity. Multiple federal and state laws regulate collection, use, and breach notification; agencies such as the Federal Trade Commission enforce consumer protection rules.
• European Union: The General Data Protection Regulation (GDPR) treats a wide range of identifiers (including quasi‑identifiers) as personal data and imposes strict processing, transparency, and transfer requirements.
• Australia: The Privacy Act regulates the handling of personal information by government and many private entities, with breach notification and sector‑specific rules.
• Canada: Federal legislation governs commercial handling of personal information, and provinces may have additional rules.

Consequences of failing to protect PII

Organizations that mishandle PII can face legal penalties, regulatory fines, litigation, financial loss, and reputational damage. High‑profile incidents have resulted in large fines and long‑term trust erosion. Individuals whose PII is exposed risk identity theft, financial fraud, and privacy harms.

What constitutes a PII violation?

A PII violation includes unauthorized access, use, disclosure, or theft of personally identifiable information. Failure to prevent breaches or to notify affected parties when required can also be a violation under applicable laws.

Major examples (illustrative)

• Large platform data misuse and breaches have exposed millions of users’ information and led to regulatory action and fines.
• Corporate data breaches have resulted in significant penalties and remediation costs for responsible organizations.

Bottom line

PII is central to privacy and security in modern life. Both individuals and organizations should limit unnecessary collection, apply strong technical and administrative controls, and follow applicable legal obligations to reduce the risk of identity theft and other harms. Robust practices—encryption, minimized data retention, access controls, user education, and incident preparedness—are the foundation of effective PII protection.