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Vol. 1 · Ed. 2026
CyberGlossary
Entry № 275

Data Breach

What is Data Breach?

Data BreachA confirmed security incident in which an unauthorised party accesses, exfiltrates, or discloses sensitive, protected, or confidential information.


A data breach occurs when an attacker bypasses controls and gains access to records that should have remained restricted, such as customer credentials, payment data, health information, or trade secrets. Common root causes include phishing, vulnerable web applications, stolen credentials, insider abuse, and supply-chain compromise. Breaches trigger regulatory notification duties under laws such as GDPR, HIPAA, and US state breach laws, and they often result in fraud, lawsuits, and lasting reputational damage. Defences combine least-privilege access, encryption of data at rest and in transit, robust logging, EDR, network segmentation, and tested incident-response and breach-notification plans.

Examples

  1. 01

    Equifax (2017): exploitation of an unpatched Apache Struts flaw exposed records of about 147 million people.

  2. 02

    Yahoo (2013-2014): compromises affecting all 3 billion user accounts.

  3. 03

    Target (2013) and Marriott/Starwood (2018): point-of-sale and reservation-system intrusions affecting hundreds of millions of customers.

Frequently asked questions

What is Data Breach?

A confirmed security incident in which an unauthorised party accesses, exfiltrates, or discloses sensitive, protected, or confidential information. It belongs to the Attacks & Threats category of cybersecurity.

What does Data Breach mean?

A confirmed security incident in which an unauthorised party accesses, exfiltrates, or discloses sensitive, protected, or confidential information.

How does Data Breach work?

A data breach occurs when an attacker bypasses controls and gains access to records that should have remained restricted, such as customer credentials, payment data, health information, or trade secrets. Common root causes include phishing, vulnerable web applications, stolen credentials, insider abuse, and supply-chain compromise. Breaches trigger regulatory notification duties under laws such as GDPR, HIPAA, and US state breach laws, and they often result in fraud, lawsuits, and lasting reputational damage. Defences combine least-privilege access, encryption of data at rest and in transit, robust logging, EDR, network segmentation, and tested incident-response and breach-notification plans.

How do you defend against Data Breach?

Defences for Data Breach typically combine technical controls and operational practices, as detailed in the full definition above.

What are other names for Data Breach?

Common alternative names include: Security breach, Information breach.

Related terms

See also