What is one of the best options for protecting mission-critical software that cannot use the latest operating system?

One of the best options for protecting mission-critical software that cannot use the latest operating system is the isolation of the software on a separate server. This practice creates a distinct environment where the software can operate without the risks associated with outdated operating systems. By isolating the software, you minimize exposure to vulnerabilities that may be present in other software or systems sharing the same environment. Being on a separate server can also limit the potential impact of a compromise, as the affected server can be more easily monitored and controlled.

Network segmentation is indeed a valuable strategy in many scenarios, as it limits communication between different network segments, which enhances security by restricting access to sensitive data and systems. However, in the context of software that cannot use the latest operating system, isolation on separate servers provides a more direct solution to mitigate risks associated with vulnerabilities in outdated software. Keeping software on a separate server helps secure legacy applications and manage their specific security needs while reducing potential points of attack.

Regular software updates are crucial for security, but if the software cannot run on the latest operating system, this option may not be applicable. Using virtual machines can be a good approach for testing or running applications in a contained environment, but it does not guarantee the same level of separation and dedicated resource allocation as