Reviewing the vendor contract should be the information security manager's first course of action when discovering an HVAC vendor has remote access to the stores to enable real-time monitoring and equipment diagnostics. The vendor contract should specify the terms and conditions of the vendor's access to the retailer's network, such as the scope, purpose, duration, frequency, and method of access. The vendor contract should also define the roles and responsibilities of both parties regarding security, privacy, compliance, liability, and incident response. Reviewing the vendor contract will help the information security manager to understand the contractual obligations and expectations of both parties, and to identify any gaps or issues that need to be addressed or resolved1. The other options are not the first course of action for the information security manager when discovering an HVAC vendor has remote access to the stores. Conducting a penetration test of the vendor may be a useful way to assess the vendor's security posture and potential vulnerabilities, but it should be done with the vendor's consent and cooperation, and after reviewing the vendor contract2. Reviewing the vendor's technical security controls may be a necessary step to verify the vendor's compliance with security standards and best practices, but it should be done after reviewing the vendor contract and in accordance with the agreed-upon audit procedures3. Disconnecting the real-time access may be a drastic measure that could disrupt the vendor's service delivery and violate the vendor contract, unless there is a clear and imminent threat or breach that warrants such action. Reference: 1: Vendor Access: Addressing the Security Challenge with Urgency - BeyondTrust 2: Penetration Testing - NIST 3: Reduce Risk from Third Party Access | BeyondTrust : Third-Party Vendor Security Risk Management & Prevention