After discovering vulnerabilities, the most effective mitigation process is to patch or update the vulnerable applications. If the application was developed in-house, a change request should be send to the development team. If neither a patch nor a fix is applicable, a compensating control should be applied. Compensating controls can consist of adding a firewall rule to block access to the vulnerable service of the application or the decision to shop around for a better product. Sometimes the compensating control can be the decision to do nothing at all. The decision of what to do depends on the criticality of the application and the specifics of the vulnerability.

ICS patch management is a complex process, largely because of the uptime requirements and the sensitive nature of the ICS equipment. Not including those found in level 3 - site operations, applications...