Network Security Audit: Methodology and Action Plan for CIOs
·2 min read·243 words
Network security audit methodology: scope, frameworks (NIST, ISO 27001, MITRE ATT&CK), testing (vulnerability assessment, penetration testing, red teaming), reporting and action plan. 2026 CIO guide.
Audit types
- Configuration audit: review of settings against best practices
- Compliance audit: NIS2, ISO 27001, PCI-DSS
- Vulnerability scanning: Qualys, Tenable, Rapid7
- Penetration testing: simulation of an external or internal attacker
- Red teaming: long-term simulated adversary engagement
- TLPT (Threat-Led Penetration Testing): mandatory under DORA
Frameworks
- NIST CSF: Identify, Protect, Detect, Respond, Recover
- ISO 27001/27002: 114 controls
- CIS Critical Controls: 18 priority controls
- MITRE ATT&CK: adversary tactics and techniques
- OWASP Top 10: web applications
Audit phases
1. Scoping
- Scope (sites, IPs, applications)
- Objectives
- Constraints (working hours, availability)
- NDA and authorization
2. Reconnaissance
- External network mapping (OSINT)
- Port scanning (Nmap)
- OS and service fingerprinting
- Vulnerability discovery
3. Exploitation
- Active testing (for penetration tests and red team engagements)
- Lateral movement
- Privilege escalation
- Data exfiltration simulation
4. Reporting
- Executive summary (1-2 pages)
- Findings with CVSS scores
- Remediation priorities
- Recommendations
- Timeline
Service providers in France
- Thales Cyber
- Capgemini Cybersecurity
- Orange Cyberdefense
- Wavestone
- Synetis
- Fireeye Mandiant
- Ernst & Young Cybersecurity
Audit budget
- Vulnerability scan: €5-15k
- Internal and external penetration testing: €20-60k
- Red team engagement: €80-200k
- TLPT (DORA): €150-500k
Recommended frequency
- Vulnerability scanning: continuous (automated tools)
- Penetration testing: at least annually (required by NIS2)
- Red team engagement: every 2-3 years
- After every major change: mandatory
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