Securing application information in a shared, system-wide search service, in which each application can register a security filtering module that is to be used at search time to filter data associated with that application. Initial, unfiltered search results are obtained based on the contents of the shared search index, and are organized by application. Previously registered filter modules are called to perform user specific, per-application filtering on the initial results, such that data to which the user issuing the search request does not have access is removed from the search results, resulting in a set of filtered search results that are presented to the user and that contain indications only of data that is accessible to the user.