What is Hardening?
Hardening is the process of reducing the attack surface of systems, applications or networks by disabling or limiting all unnecessary functions, services, permissions and configurations.
The aim is to make systems as resilient as possible against cyberattacks, misconfigurations and unwanted access.
🧱 What does hardening involve?
Hardening consists of multiple layers, including:
- Operating system hardening (Windows, Linux)
- Network hardening (firewall rules, ports)
- Application hardening (web servers, databases)
- OT system hardening (e.g. PLC, SCADA, HMI)
- Cloud hardening (IAM, storage, APIs)
🔧 Examples of hardening measures
| Domain | Measure |
|---|---|
| OS | Removing unused services and users |
| Network | Closing unused ports, restricting broadcast traffic |
| Application | Disabling debug modes, configuring secure headers |
| User management | RBAC, MFA, password policy and account lockout |
| Logging & auditing | Enabling SIEM, logging of critical events |
| Patch management | Regular application of security updates |
| OT | Firmware hardening, restricting remote access, applying Air gap |
📋 Best practices
- Use official hardening guidelines, such as:
- CIS Benchmarks (Center for Internet Security)
- DISA STIGs (US DoD)
- IEC 62443 for industrial systems
- Document and version-control all hardening actions
- Combine with Vulnerability Management and penetration testing
- Automate via hardening scripts or configuration management (Ansible, SCCM)
✅ Benefits
- Improved security against unauthorised access
- Fewer vulnerabilities and reduced exploit potential
- Compliance with standards such as ISO 27001, NIS2, BIO, IEC 62443
- Lower management overhead thanks to fewer unused components
📌 In summary
Hardening is the process of systematically slimming down and securing systems and applications in order to minimise risk. It is a fundamental step within Defense in Depth and a prerequisite for any secured IT or OT environment.