Definition
System hardening reduces attack surface:
\text{Attack surface} = \sum_i \text{Exposed vulnerabilities}_i
In SCU terms: Hardening eliminates unnecessary χ-mode pathways—reducing the ways attackers could cause unauthorized state transitions.
Principle of Minimization
Every capability is potential vulnerability:
\text{Less code} \rightarrow \text{Fewer vulnerabilities}
\text{Less access} \rightarrow \text{Smaller attack surface}
Hardening Techniques
| Technique | χ-Mode Effect |
|---|---|
| Remove unused services | Eliminate χ-mode entry points |
| Apply patches | Fix known χ-mode vulnerabilities |
| Secure configurations | Constrain χ-mode options |
| Restrict privileges | Limit χ-mode access |
| Enable logging | Record χ-mode activity |
Areas to Harden
| Component | Hardening Focus |
|---|---|
| OS | Kernel, services, accounts |
| Network | Firewall, ports, protocols |
| Applications | Input validation, permissions |
| Database | Access controls, encryption |
Configuration as Defense
Default configurations prioritize convenience:
\text{Defaults} \neq \text{Secure}
Hardening adjusts configurations for security over convenience.
Measuring Attack Surface
A = \sum_i (\text{Exposure}_i \times \text{Severity}_i)
Reduce by:
- Disabling exposed components
- Limiting accessibility
- Adding protective layers
Maintenance
Hardening is ongoing:
- New vulnerabilities discovered
- Configuration drift occurs
- Systems change over time
The Key Insight
Hardening minimizes χ-mode attack surface.
Security through reduction:
- Every feature is potential vulnerability
- Remove what isn't needed
- Constrain what remains
- Monitor what operates
A hardened system has fewer χ-mode pathways an attacker could exploit—because unnecessary capabilities have been eliminated.