A breach notification letter is an official communication sent by an organization to individuals whose personal data has been compromised in a security incident, such as a data breach. The letter typically outlines the nature of the breach, the types of information affected, potential risks, and recommended steps for recipients to protect themselves. It may also include information about what the organization is doing to address the breach and prevent future incidents. Breach notification letters are often required by law or regulation, such as the GDPR or HIPAA, to ensure transparency and help affected individuals take necessary precautions.