A service sunset is the planned retirement of an online product, feature, or platform. In cyber security, it matters because online services depend on authentication, update channels, APIs, and account systems that must be maintained until the final shutdown. A sunset is not just “turning something off”; it is a managed transition that should include notice, data handling, identity migration, and a clean end state for users and operators.
Sunsets appear in real environments when older devices, apps, or integrations are no longer supported and must be moved to newer versions or platforms. They also create security risk if communication is unclear: attackers may use fake migration guides, spoofed support pages, or malicious downloads to exploit confused users. Defenders reduce that risk by publishing clear timelines, validating update paths, preserving account access rules, and removing unsupported components in a controlled way. Good sunset planning helps limit fraud, access errors, and trust breakdowns during retirement.