1. A virus scan system, comprising: a full scanning system for performing a full scan of each file in a local file system; a file inventory system for inventorying each file in the local file system and generating a set of current inventory records, wherein each current inventory record includes a unique key of the associated file, a complete filename of the associated file, and a signature of the associated file; wherein the unique key includes a hash code of the complete filename of the associated file, and the signature includes a timestamp of a last modification of the associated file and a size of the associated file; a system for interfacing with a server to store and retrieve an existing set of inventory records stored on the server; an inventory compare system for comparing the current set of inventory records with the existing set of inventory records to identify files in the local file system that were modified since the existing set of inventory records was generated, wherein a file is identified as modified if the signature for the file in the current set of inventory records does not match the signature for the file in the existing set of inventory records such that at least a size of the file in the current set of inventory records is different from a size of the file in the existing set of inventory records; and a selective scanning system for selectively scanning only files in the local file system that were identified as modified by the inventory compare system; wherein, in the case that a record of the current set of inventory records is included at the local file system and not included in the existing set of inventory records on the server, the selective scanning system selectively scans the file associated with the record not included in the existing set of inventory records and located at the local file system, and the system for interfacing with the server submits a request to the server to update the existing set of inventory records stored on the server to indicate that the selective scanning of the file associated with the record not included in the existing set of inventory records and located at the local file system has occurred.