Data breach, or data leak, is a situation when information that is not supposed to be available to exit the company in any form becomes available for an outside person. A data leak occurs when information has been extracted or stolen from a system without the owner's knowledge or permission. A small company or large organization can be affected by a data breach. Stolen data may include confidential, proprietary, or sensitive information such as credit card numbers, customer data, trade secrets, or national security issues.