The Chief Information Security Officer (CISO) of a power generation facility is concerned about being able to detect missing security updates on the critical infrastructure in facility. Most of this critical infrastructure consists of ICS and SCADA systems that are maintained by vendors, and the vendors have warned the CISO that proxying network to cause a DoS condition. Which of the following would be BEST to address the CISOs concerns while keeping the critical systems functional?

A. Configuring the existing SIEM to ingest all log files properly

B. Implementing a passive vulnerability scanning solution

C. Deploying a data diode for internal websites

D. Adding more frequent antivirus and anti-malware signature updates

E. Adjusting file access rules to use the concept of least privilege