Which of the following is NOT a step in the operations security process?

In the context of operations security (OPSEC), the correct response highlights that estimation of costs is traditionally not considered a core step in the OPSEC process. The primary goal of OPSEC is to protect critical information from adversaries, which involves a systematic approach.

The other options represent essential components of the OPSEC process. For instance, the application of countermeasures is crucial as it involves implementing strategies to mitigate risks associated with identified vulnerabilities. Analyzing vulnerabilities is an important step, as it helps in understanding potential exposure points for sensitive information. Lastly, the identification of critical information is foundational in OPSEC, as it determines what specific data needs protection in order to maintain an organization's operational security.

These foundational activities focus on the protection of information rather than assessing the costs associated with implementing security measures, which distinguishes them from the cost estimation process. Hence, focusing on the critical information and embedding the necessary protective steps reflects the true nature of operations security, while cost estimation remains a separate organizational concern rather than a direct OPSEC activity.