A method and system for operating a network server to discourage inappropriate use are disclosed. The method provides for altering files on the server in such a way so as essentially not affect acceptable, desired file types in any noticeable way, and to substantially corrupt undesirable file types. The method may be applied to every file copied to or from a memory of the server. In the alternative, the method may be applied only to selected files or types of files on the server. In particular, the files corrupted by altering according to the invention are executable software files and compressed files, that are generally not fault-tolerant. Fault tolerant files, such as uncompressed text and graphics files in common Internet-compatible formats, are not noticeably affected. The network server will therefore no longer be useful for storing or transferring undesirable files, and such use will be discouraged. According to a related embodiment of the invention, a system comprises a server having an application that performs one of the embodiments of the method according to the invention.