OnSystem Defender is an application hardening and endpoint security agent for Windows that operates using a patent-pending In-Memory Application Reference Monitor. Rather than detecting known malware signatures or monitoring external threat indicators, it enforces application behavior from within each running process by learning normal internal code path patterns and blocking any deviations. The agent loads into all running software without requiring source code access or changes to development environments. It establishes behavioral baselines through self-learning on production, trusted, and QA systems, then enforces those baselines in real time to prevent unauthorized code execution paths. Key protections include defense against malware hiding inside legitimate applications, mitigation of zero-day exploits, protection against unpatched and unpatchable vulnerabilities, and resistance to ransomware. The product also provides application-layer access control (whitelisting) that is designed to be more resistant to bypass than traditional EPP and EDR solutions, which it claims can be circumvented without detection. OnSystem Defender is managed via a central Management Console used to deploy policies to workstations and servers. Pre-configured policies can be applied broadly with minimal customization. OnSystem Logic monitors for new or unknown application behaviors and delivers notifications with impact statements within 24 hours. The product targets enterprise environments and is designed to be transparent to end users with no reported performance impact. It functions on devices both on and off the network.