Availability in Information Security

Availability is the third and final pillar of the [CIA Triad](/en/computer/d/ciatriad). It ensures that authorized users, systems, and processes can access and use information assets and systems promptly when needed, without delay or disruption.

1. Goal of Availability

The main goal is to minimize downtime. This means protecting the service from all forms of disruption, including system failures, natural disasters, and malicious external attacks.

Example:
- Ensuring a financial trading platform operates smoothly 24/7.
- Guaranteeing that users can access a website even if one server is overloaded or a network segment fails.

2. Key Technologies and Measures for Availability

Measures to achieve availability are grouped into Prevention (Fault Tolerance) and Recovery/Response.

① Prevention and Fault Tolerance

Increasing the robustness of the system to decrease the likelihood of failure.

Redundancy: Duplicating critical components and functions.
- Example: Using a Load Balancer to distribute traffic across multiple servers, ensuring that if one server fails, others can take over seamlessly .
Clustering: Grouping multiple servers to work as a single, highly available system.
Backup Power: Implementing UPS (Uninterruptible Power Supplies) and emergency generators.

② Recovery and Response

Quickly restoring service and data after a failure occurs.

Backup and Recovery Planning (DRP): Regularly backing up data and having a clear Disaster Recovery Plan to restore services quickly after an incident.
Patch Management: Proactively patching systems and software to prevent security exploits that could lead to service outages.
Monitoring: 24/7 surveillance of server, network, and application health to detect failure signs early.

③ Defense Against External Threats

Defending against attacks specifically targeting availability.