Organizations continue to deploy firewalls as their central gatekeepers to prevent unauthorized users from entering their networks. However, network security is in many ways similar to physical security in that no one technology serves all needs - rather, a layered defense provides the best results. Organizations are increasingly looking to additional security technologies to counter risk and vulnerability that firewalls alone cannot address. Intrusion detection systems (IDS) provide around-the-clock network surveillance. They analyze the packet data streams within the network, searching for unauthorized activity, such as attacks by hackers, enabling users to respond immediately to security breaches. Using a physical analogy, IDS systems are equivalent to video cameras and motion sensors; they detect unauthorized or suspicious activity.The Catalyst 6500 and Cisco 7600 Intrusion Detection Module provides real-time, around-the-clock network surveillance. Designed to address the increased requirements for security visibility, denial-of-service protection, antihacking detection, and e-commerce business defenses, the IDS module monitors network traffic off the switch backplane and alarms on malicious or unauthorized activity.