A computer gateway for an intranet of computers, including a scanner for scanning incoming files from the Internet and deriving security profiles therefor, the security profiles being lists of computer commands that the files are programmed to perform, a file cache for storing files, a security profile cache for storing security profiles for files, and a security policy cache for storing security policies for client computers within an intranet, the security policies including a list of restrictions for files that are transmitted to intranet computers. A method and a computer-readable storage medium are also described and claimed.