An automatic method for rating data files for objectionable content in a distributed computer system includes preprocessing the file to create semantic units, comparing the semantic units with a rating repository containing entries and associated ratings, assigning content rating vectors to the semantic units, and creating a modified data file incorporating rating information derived from the content rating vectors. For text files, the semantic units are words or phrases, and the rating repository also contains words or phrases with corresponding content rating vectors. For audio files, the file is first converted to a text file using voice recognition software. For image files, image processing software is used to recognize individual objects and compare them to basic images and ratings stored in the rating repository. In one embodiment, a composite content rating vector is derived for the file from the individual content rating vectors, and the composite content rating vector is incorporated into the modified file. In an alternate embodiment, semantic units with content rating vectors exceeding preset user limit values of objectionable content are blocked out by display blocks or, for audio, audio blanking signals, for example, beeps. The user can then view or hear the remaining portions of the file. The invention can be used with any type of data file that can be divided into semantic units, and can be implemented in a server, client, search engine, or proxy server.