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Risk R-004 - Exposure of internal services due to firewall misconfiguration

FieldValue
Risk IDR-004
AssetOPNsense Firewall (Platform – Owner: Sec)
ScenarioS-003 - Exploitation of firewall misconfiguration
Likelihood🟨 Medium - misconfigurations are common, especially after updates or manual rule changes
Impact🟥 High - unauthorized external access may allow compromise of sensitive internal services and lateral movement
Risk Level🟥 High
OwnerSec
Last Review2026-03-08
Next Review2026-09-08

Associated Controls:

  • Review and enforce firewall rule set regularly.
  • Apply principle of least privilege for all inbound/outbound traffic.
  • Conduct firewall change management with peer review.
  • Monitor and alert on anomalous traffic patterns.
  • Implement network segmentation to contain potential lateral movement.

References:

  • ISO 27001 - Control 5.1 Policies for information security.
  • ISO 27001 - Control 8.20 Network security.
  • ISO 27001 - Control 8.22 Segregation of networks.
  • NIST CSF - PR.AC Identity Management, Authentication and Access Control.
  • NIST CSF - PR.PT Protective Technology.
  • NIST CSF - ID.AM Asset Management.
  • EBIOS RM - Analysis of risks related to network exposure and misconfiguration.

Response Actions:

  • Containment - Temporarily restrict exposed ports or quarantine affected subnet.
  • Eradication - Correct misconfigured rules and remove any unauthorized access points.
  • Recovery - Verify internal systems and restore secure connectivity.
  • Post-incident - Review firewall change logs, update configuration standards, and conduct training if misconfiguration was human error.