1. A file system comprising: a digitally signed file system in which data, metadata and files are objects, each object having a globally unique and content-derived fingerprint and wherein object references are mapped by the fingerprints; the file system having a root object comprising a mapping of all object fingerprints in the file system; wherein a change to the file system results in a change in the root object, and tracking changes in the root object provides a history of file system activity.