Security from malicious attack is provided for a user environment running in a virtualized environment by a virtual security appliance (VSA) running outside of the user environment, but on the same computer system as the user environment. For example, a VSA running in a virtual machine can provide security for a user environment running in a second virtual machine. The separation of the VSA from the user environment enhances the robustness of the VSA against malicious attacks seeking to disable/bypass the protections of the VSA, while avoiding the costs and complexities of a physical security appliance.