Quick Spam Filter

Current version: 1.2.23 (6 July 2025) [src]

Quick Spam Filter (QSF) is an email classification filter, designed to be small, fast, and accurate, which works to classify incoming email as either spam or non-spam.

To recognise spam, QSF strips the text out of the email (using MIME decoding and HTML stripping) and then splits it into tokens (words, word pairs, URLs, and so on). These tokens are then looked up in a database and analysed using the Bayesian technique to see whether the email should be classified as spam or not.

The database is generated by a process of training - QSF is given two mailboxes, one containing known spam, and the other containing known non-spam, to train itself on. After training, if QSF misfiles any email, the message it got wrong can be fed back into the database, allowing QSF to learn from its mistakes.

For a more in-depth look at the way in which QSF tokenises and classifies messages, please see the "Technical details" section of the manual.

QSF is designed to be run by an MDA, such as procmail. See the FAQ for a quick-start guide.

This software is distributed under the terms of the Artistic License 2.0.

To install qsf, follow these steps:

curl -O https://ivarch.com/s/qsf-1.2.23.tar.gz
tar xzf qsf-1.2.23.tar.gz
cd qsf-1.2.23
sh ./configure
make
sudo make install

Comments, bug reports, and patches can be sent using the Issue tracker, or through the Contact Form.

News

1.2.23 - 6 July 2025

1.2.15 - 29 March 2021

1.2.11 - 3 January 2015

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