Field validation is testing a security method in realistic operating conditions to determine whether it works as intended without causing unacceptable disruption or harm. Unlike a review limited to plans or simulations, it assesses how a control behaves within the systems, workloads, and constraints where it will actually be used.
In operational technology (OT), field validation matters because security changes can affect availability, timing, and physical safety. Defenders may test a proposed access policy or monitoring control in a controlled deployment, check its effect on operations, and adjust it before wider use. Testing should account for failure conditions and document results, limitations, and remaining risk. A successful test supports a decision; it does not prove that a method is safe in every environment.