Availability represents the final pillar of information security, ensuring that “the data is available when the system says it will” with timeframes ranging from immediate access to several days, depending on system requirements.
Multi-Layer Implementation
Effective availability requires management across three layers:
Network Layer: Controls request handling capacity through firewalls, load balancing, and network sizing. Distributed denial-of-service attacks deliberately overwhelm systems by flooding networks and servers with excessive requests.
Server Layer: Optimizes processing power, memory, and disk allocation. Running only necessary processes allows servers to dedicate resources efficiently and minimizes security risks.
Application Layer: Implements three key strategies:
- Access Controls: Preventive measures that manage resource consumption by restricting unauthorized access to application components
- Input Validation: The initial defensive strategy that restricts data types and quantities, requiring validation at multiple trust boundaries
- Resource Management: Establishes constraints on file uploads, simultaneous logins, and data consumption to prevent denial-of-service conditions
Implementation Strategy
Successful availability requires understanding intended contexts, user types, and temporal requirements. This foundational knowledge enables teams to architect systems with appropriate controls matching organizational goals.