A data theft incident is a security event in which information is suspected to have been accessed, copied, or removed without authorization. The data may still exist in the original system, but the key concern is that an attacker or unauthorized party has obtained a usable copy.
This matters because stolen data can fuel phishing, impersonation, fraud, credential attacks, and extortion. In practice, these incidents often involve sensitive records such as employee details, customer data, health information, or configuration files. The risk is especially high when the exposure comes through a third-party application, cloud integration, or other trusted access path, because defenders may not immediately see the theft or the full scope of access.