Which of the following would help improve data security on a Windows Server?

Employing NTFS file permissions is an effective way to improve data security on a Windows Server. NTFS, or New Technology File System, allows for detailed and granular control over file and folder permissions. This means that administrators can specify who has access to specific files and folders, what they can do with that access (such as read, write, or execute), and can even apply permissions at different levels, including inheritances and exceptions.

By implementing NTFS permissions, sensitive data can be effectively protected from unauthorized access. This type of security is critical in a server environment where multiple users may have access, as it helps ensure that only those who need access to particular information are granted that ability. It provides a structured way to protect the integrity and confidentiality of data stored on the server.

While other options could contribute to security, they do not directly enhance user access control in the same way that NTFS permissions do. Using a public network connection exposes the server to greater risks of unauthorized access, while removing all user access would render the server unusable for legitimate users. Backing up files on a USB drive can help with data recovery but does not address the prevention of unauthorized access to the data itself.