A software security application for a Windows® OS based electronic computer system provides an isolated User environment which protects a User from unauthorized access to and manipulation of data on the system. The security software implements an isolated User file system and provides process/IPC isolation, Windows® registry isolation, network interface isolation, and isolated administrative control on the computer system. Interactive components of the system include an execution hook component that traps system calls, a job object component that creates/destructs, manages and manipulates job objects, a system call hook component for trapping and filtering all Windows registry I/O requests, a file system block device driver for mounting/unmounting the isolated User file system, a file system/filter driver, a network interface/NDIS hook component, and an environment handler. The environment handler provides the overall management interface for other system components, allowing definition of rules, managing authentication and other control/management functions.