1. A security system for securing files from unauthorized access within a distributed computer network, the security system comprising: a processor; and a memory storing a plurality of client modules, comprising at least computer program code stored on a computer readable medium, the plurality of client modules configured to operate on respective user computers, and configured to control access to secured files having access rules in a header portion thereof, wherein some or all of at least a portion of security policy information that governs a type, a location, a duration, and an extent of access to the secured files that are permitted by users via the respective user computers is received at respective ones of the plurality of client modules from a central service module via a local service module comprising a delivery queue for temporarily storing security policy change messages to be delivered to client modules determined to be inactive and affected by a security colic change received at the central service module.