A security auditor is reviewing vulnerability scan data. Which of the following BEST indicates that valid credentials were used during the scan?

The indication that valid credentials were used during a vulnerability scan is best reflected by the ability of the scan to enumerate software versions of installed programs. When valid credentials are applied during the scanning process, the scanning tool can access deeper system information, including specific software versions, configurations, and the overall status of applications installed on the systems. This sort of detailed information often requires authenticated access, as many applications do not expose their versions and configurations through unauthenticated scans.

While open ports, protocols, and services being exposed could provide information about the network configuration of a host, this data can often be gathered without the need for valid credentials. Similarly, while producing a list of vulnerabilities is certainly valuable, that's a more general output that may not require authentic access; many vulnerabilities can be identified using unauthenticated scans based on known issues with exposed services or software. The identification of expired SSL certificates is another finding that can be revealed without authenticated access, as these details are typically available to any party accessing the service over the network.

In contrast, the ability to enumerate specific software versions is a strong indicator of successful authenticated access, demonstrating the effectiveness and thoroughness of the scanning process when conducted with valid credentials.