What strategies do you implement to ensure the security of operational legacy systems?

This question aims to evaluate your knowledge of legacy systems and their security issues as well as your ability to manage their protection. The interviewer wants to know how you handle these older systems, which are critical to daily operations but may not have been designed with current security threats in mind. When answering, consider the following items:

1. Any past experience you have with ensuring the security of legacy systems.
2. Any specific strategies you've used or are aware of.
3. How you adapt these strategies based on the specifications and risks associated with a given system.

In my previous role, I worked with several legacy systems, and my approach to their security involved a multi-layered strategy. I believe with aging technology, it is important to create tiers of defense. Therefore, one of my strategies involved installing a network intrusion detection system which monitored the traffic and alerted for any malicious activities. Secondly, I also made sure each of these systems operated on a separate network classification, thus providing another layer of protection.

However, I didn't stop there because security isn't a one-time operation. It involved continuous monitoring and assessment. A vital part of my security plan involved regular checks to ensure patches and updates were installed promptly. Besides, I always encrypted sensitive data on these systems and regularly trained staff on security practices, as human error can be a significant risk. Working this way, I was able to adequately secure our legacy systems despite their inherent limitations.

In my experience securing operational legacy systems, I use a combination of preventive and reactive strategies. To begin, I'd conduct a complete risk assessment of the legacy system to identify any potential vulnerabilities. Knowing the system’s weaknesses makes it easier to take preventative action.

My next step would be to ensure that all systems are up-to-date with the latest patches and updates. This can pose a challenge in legacy systems, so a workaround would be to implement virtual patching to shield vulnerabilities without disturbing the stability or functionality of the systems.

Another critical area is securing our data, which I do by enforcing strict access controls, ensuring only authorized individuals have access to sensitive information. I also ensure to implement strong data encryption.

Lastly, constant monitoring and regular auditing of security logs is a part of my strategy. This helps in identifying and addressing issues before they escalate. By doing this, I’ve been able to mitigate various security risks associated with operational legacy systems."