Intrusion Detection Systems (IDSs) are integral to safeguarding networks by detecting and responding to threats from malicious traffic or compromised devices. However, standalone IDS deployments often fall short when addressing the increasing complexity and scale of modern cyberattacks. This paper proposes a Collaborative Intrusion Detection System (CIDS) that leverages Snort, an open-source network intrusion detection system, to enhance detection accuracy and reduce false positives. The proposed architecture connects multiple Snort IDS nodes to a centralised node and integrates with a Security Information and Event Management (SIEM) platform to facilitate real-time data sharing, correlation, and analysis. The CIDS design includes a scalable configuration of Snort sensors, a centralised database for log storage, and LogScale SIEM for advanced analytics and visualisation. By aggregating and analysing intrusion data from multiple nodes, the system enables improved detection of distributed and sophisticated attack patterns that standalone IDSs may miss. Performance evaluation against simulated attacks, including Nmap port scans and ICMP flood attacks, demonstrates our CIDS's ability to efficiently process large-scale network traffic, detect threats with higher accuracy, and reduce alert fatigue. This paper highlights the potential of CIDS in modern network environments and explores future enhancements, such as integrating machine learning for advanced threat detection and creating public datasets to support collaborative research. The proposed CIDS framework provides a promising foundation for building more resilient and adaptive network security systems.