A firewall between internal network segments improves security and reduces risk by inspecting all traffic flowing between network segments and applying security policies. This will prevent unauthorized or malicious access, data leakage, or network attacks from compromising the network resources or data. Logging all packets passing through network segments may provide audit trails and evidence, but not prevent or mitigate security incidents. Monitoring and reporting on sessions between network participants may help to identify anomalous or suspicious activities, but not block or filter them. Ensuring all connecting systems have appropriate security controls enabled may enhance the overall network security posture, but not isolate or segregate different network segments. References: Info Technology & Systems Resources | COBIT, Risk, Governance ... - ISACA, section "Book COBIT 2019 Design Guide: Designing an Information and Technology Governance Solution | Digital | English"