Network-centric computing aims to solve the problems associated with traditional client/server systems, namely the high performance requirements, and costly maintenance of, the computing resources. With the network-centric model, applications are stored on servers and downloaded to clients as required, where they are then executed locally. User data is saved back to the remote server - local user data is only temporary. However these applications lack a standard file system where they can store their data files. For instance, when these applications are run as Java applets in a web browser, they are prevented from accessing the local storage system by the Java environment. This paper proposes the Java File System (JFS), a distributed file system for use by these applications, which provides strong security and client/server heterogeneity.