The correct answer is 'Implement a rigorous patch management policy' because it addresses the direct cause of the incident, which was the exploitation of outdated software. This recommendation aims to prevent similar incidents by ensuring that all software is regularly updated to patch known vulnerabilities. 'Increasing data encryption efforts' might improve security but doesn't address the root cause of the incident. 'Conducting more frequent staff meetings' is non-specific and doesn't provide a strategic approach to preventing a similar incident. 'Upgrading the physical security' may be necessary in some contexts, but in this case, the incident was due to software exploitation, not a physical security breach.