To address concerns about confidential files on personal devices, what solution should John implement?

Implementing a solution that focuses on blocking file downloads on Slack's mobile app effectively addresses concerns about the safety of confidential files on personal devices. This approach minimizes the risk of sensitive information being stored or accessed on personal devices, which may not have the same level of security controls as corporate devices. By preventing file downloads on the mobile app, organizations can ensure that confidential documents remain within a controlled environment, accessible only through secure channels, thereby reducing the potential for data leakage or unauthorized access.

Enabling file expiration settings, while a useful feature, does not directly prevent files from being downloaded onto personal devices. Similarly, limiting mobile app usage can restrict access to Slack, but it does not specifically address the issue of keeping confidential files secure when accessing the app. Disconnecting personal devices from corporate networks could be a drastic measure and may hinder remote work flexibility without directly mitigating the dangers posed by confidential files being downloaded to personal devices.