Definition
Availability
Availability is the security property that ensures systems and data are accessible and usable upon demand by an authorised entity. It guarantees that resources remain operational and reachable despite faults, attacks, or high load.
Threats
Availability can be compromised by:
- Denial-of-service attacks: Overwhelming resources to prevent legitimate access
- Hardware failures: Component malfunctions causing system downtime
- Software defects: Bugs or crashes rendering services unusable
- Natural disasters: Physical destruction of infrastructure
Mechanisms
Ensuring Availability
Common mechanisms include redundancy, failover systems, load balancing, and disaster recovery protocols.