Which action is effective in ensuring a critical application's security before deployment?

Conducting a static code analysis is an effective action to ensure a critical application's security before deployment. This process involves analyzing the application's source code without executing it to identify potential vulnerabilities, coding errors, or security weaknesses. Static code analysis tools can help developers catch issues early in the development lifecycle, allowing them to correct these problems before the application is deployed in a live environment. This proactive approach to identifying security flaws contributes significantly to the overall security posture of the application.

In contrast, while user training on security policies, applying encryption methodologies, and implementing simple access controls are all important security measures, they are more about protecting the application or its users after deployment rather than assessing the application's security prior to release. User training focuses on educating personnel on how to handle security issues, encryption methodologies are used to protect data in transit or at rest, and access controls help secure the application's operational environment. None of these actions specifically address vulnerabilities within the code or ensure that the application itself is secure before it is made available for use.