A kill file (also killfile, bozo bin or twit list) is a file that stores text matching patterns that are used in some Usenet reading programs to filter out (ignore) articles by subject, author, or other header information.
Adding a pattern to a kill file results in matching articles being ignored by the person using the newsreader.
For example, articles might score as ignored (killed) if it violates too many low-weighted stylistic rules (e.g. containing too many capital letters or too little punctuation, implying an annoying reading experience), or only one or two highly-weighted rules (such as the body containing objectionable keywords or the origin being a known source of spam).
[2] Jerry Pournelle wrote in 1986 of his wish for improvements to an offline reader for the Byte Information Exchange online service: "What I really need, though, is a program that will ... sort through the messages, assigning some to a priority file and others to the bit bucket depending on subject matter and origin".
[3] In William Gibson's novel Idoru, the virtual community Hak Nam is built around an "inverted killfile" and is modeled on Kowloon Walled City.