Which of the following should a company use to provide proof of external network security testing?

Third-party attestation is the correct answer because it involves an independent organization reviewing and verifying a company's security controls and practices, providing credible proof of external network security testing. This is often done through audits or certifications like SOC 2. A Business Impact Analysis (BIA) identifies critical business functions and the impact of disruptions, but doesn't prove security testing. Supply Chain Analysis focuses on risks within the supply chain, not direct proof of a company's external network security testing. A Vulnerability Assessment identifies security weaknesses but doesn't provide the independent, verifiable proof that a third-party attestation offers.