A ledger in cybersecurity refers to a permanent, chronological digital record that logs transactions, events, or data changes within a system. This record is often immutable, meaning that once information is entered, it cannot be altered or deleted. Ledgers are commonly used for auditing, compliance, and tracking activities, providing transparency and accountability. In the context of blockchain technology, a distributed ledger is maintained across multiple nodes, ensuring that all participants have a synchronized and tamper-resistant record. Ledgers help organizations detect unauthorized activities, support forensic investigations, and ensure data integrity by maintaining a trustworthy history of all actions performed within a digital environment.