Security Audits: Internal, External, Third-Party, and How to Report Findings

Security audits are systematic examinations of an organisation's security controls, policies, and procedures to determine whether they are effective, appropriate, and compliant with applicable requirements. The CISSP exam tests the types of audits, the metrics used to measure security programme effectiveness, how findings are reported and managed, and the obligations around ethical disclosure.

Types of Security Audits

Security audits can be conducted by internal teams, external firms, or regulators, and each has distinct characteristics, strengths, and use cases.

Internal audits are conducted by the organisation's own audit or security team. They are typically less expensive than external audits, can be more frequent, and provide valuable ongoing monitoring of the security programme. However, internal audits may be perceived as less objective because the auditors may be reluctant to report findings that reflect poorly on their own organisation or colleagues. Independence is critical: the internal audit function should report to the board or audit committee, not to the CISO or IT leadership.

External audits are conducted by independent third parties. They provide objectivity and independence that internal audits may lack. External auditors bring fresh perspectives and may identify issues that internal teams have normalised. External audits are often required for regulatory compliance (SOX, HIPAA, PCI DSS) and for obtaining certifications (ISO 27001, SOC 2). They are typically more expensive and less frequent than internal audits.

Third-party audits of vendors and suppliers assess whether third parties that have access to the organisation's data or systems meet acceptable security standards. Rather than each customer independently auditing every vendor, standardised third-party audit frameworks (SOC 2, ISO 27001) allow vendors to undergo a single audit whose results can be shared with multiple customers.

Regulatory audits are conducted by government agencies or industry regulators to verify compliance with specific regulatory requirements. These include banking regulators (OCC, FDIC), healthcare regulators (OCR for HIPAA), and securities regulators (SEC). Regulatory audits carry significant consequences: violations can result in fines, consent decrees, or operational restrictions.