An Intrusion Prevention System is technology that looks at network (e.g. Internet) traffic to detect security threats like unwanted access. In Norton device security, the Intrusion Prevention System (IPS) works together with the Smart Firewall to detect malware and intrusions from network traffic. The Intrusion Prevention System inspects traffic in a much deeper way than the Smart Firewall. Once the Smart Firewall lets permitted traffic in, IPS carefully examines the contents of the traffic that comes through.