A kill file (also killfile, bozo bin or twit list) is a per-user file used by some Usenet reading programs (originally Larry Wall's rn) to discard summarily (without presenting for reading) articles matching some unwanted patterns of subject, author, or other header lines.
Thus to add a person (or subject) to one's kill file is to arrange for that person to be ignored by one's newsreader in the future. By extension, it may be used for a decision to ignore the person or subject in other media. Sometimes more than one kill file will be used. Some newsreader programs also allow the user to specify a time period to keep an author in the kill file.
Newer newsreader software like Gnus often provides a more advanced form of filter known as a score file, which can use multiple rules to determine which articles are shown. Web-based forums usually have a similar feature called ignore list, which hides any posts sent by users on the list.
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.