What is a "data breach"?

A data breach occurs when sensitive information, such as passwords, financial details, or personal records, is accessed, stolen, or exposed without authorization, whether through hacking, a misconfigured database left open on the internet, or an employee mistake. Large breaches at major companies can expose the personal data of millions of customers simultaneously, since so much information is now stored digitally in centralized systems that, once compromised, can leak enormous amounts of data all at once.

A crack in a hard drive is a physical hardware defect, unrelated to unauthorized access of information, and a slow internet connection is simply a performance issue with no connection to data security or privacy at all.

After a major breach, security experts commonly recommend changing passwords not just on the affected service but anywhere you reused that same password, since attackers often try leaked password and email combinations across many other websites, a technique called credential stuffing.