A computer network endpoint is secured to prevent information leak or other compromise by instantiating in memory first, second and third security zones. With respect to an authorized user, the first zone is readable and writable, the second zone is read-only, and the third zone is neither readable nor writable. System information (e.g., applications, libraries, policies, etc.) are deployed into the first zone from the second zone. When sensitive data is generated in the first zone, e.g., when a secure communication session is established using a cryptographic key, the sensitive data is transferred from the first zone to the third zone, wherein it is immune from information leak or other compromise. The sensitive information is transferable from the third zone to one or more external having a need to know that information. Because information does not pass directly from the first security zone to the external systems, the endpoint is secured against information leak or other attack.