#!/usr/bin/perl -w -T use strict; use File::Spec; # Do 'use vars' instead of my() since CmdLearn looks for these and my() # makes them non-exportable. Doh. use vars qw/ $PREFIX $DEF_RULES_DIR $LOCAL_RULES_DIR /; $PREFIX = '@@PREFIX@@'; # substituted at 'make' time $DEF_RULES_DIR = '@@DEF_RULES_DIR@@'; # substituted at 'make' time $LOCAL_RULES_DIR = '@@LOCAL_RULES_DIR@@'; # substituted at 'make' time use lib '@@INSTALLSITELIB@@'; # substituted at 'make' time BEGIN { # Locate locally installed SA libraries *without* using FindBin, which generates # warnings and causes more trouble than its worth. We don't need to be too # smart about this BTW. my @bin = File::Spec->splitpath($0); my $bin = ($bin[0] ? File::Spec->catpath(@bin[0..1]) : $bin[1]) # /home/jm/foo -> /home/jm || File::Spec->curdir; # foo -> . # check to make sure it wasn't just installed in the normal way. # note that ./lib/Mail/SpamAssassin.pm takes precedence, for # building SpamAssassin on a machine where an old version is installed. if (-e $bin.'/lib/Mail/SpamAssassin.pm' || !-e '@@INSTALLSITELIB@@/Mail/SpamAssassin.pm') { # These are common paths where the SA libs might be found. foreach (qw(lib ../lib/site_perl ../lib/spamassassin ../share/spamassassin/lib)) { my $dir = File::Spec->catdir($bin, split('/', $_)); if(-f File::Spec->catfile($dir, "Mail", "SpamAssassin.pm")) { unshift(@INC, $dir); last; } } } } require Mail::SpamAssassin::CmdLearn; exit Mail::SpamAssassin::CmdLearn::cmdline_run (); # --------------------------------------------------------------------------- =head1 NAME sa-learn - train SpamAssassin's Bayesian classifier =head1 SYNOPSIS B [options] [file]... B [options] --dump [ all | data | magic ] Options: --ham Learn messages as ham (non-spam) --spam Learn messages as spam --forget Forget a message --rebuild Rebuild the database if needed --force-expire Force an expiry run, rebuild every time --dump [all|data|magic] Display the contents of the Bayes database Takes optional argument for what to display --dbpath For dump only, specifies (in bayes_path form) where to read the Bayes DB from --regexp For dump only, specifies which tokens to dump based on a regular expression. -f file, --folders=file Read list of files/directories from file --dir Ignored; historical compatability --file Ignored; historical compatability --mbox Input sources are in mbox format --showdots Show progress using dots --no-rebuild Skip building databases after scan -L, --local Operate locally, no network accesses -C file, --config-file=file Path to standard configuration dir -p prefs, --prefs-file=file Set user preferences file -D, --debug-level Print debugging messages -V, --version Print version -h, --help Print usage message =head1 DESCRIPTION Given a typical selection of your incoming mail classified as spam or ham (non-spam), this tool will feed each mail to SpamAssassin, allowing it to 'learn' what signs are likely to mean spam, and which are likely to mean ham. Simply run this command once for each of your mail folders, and it will ''learn'' from the mail therein. Note that I in the mail folder names is supported; in other words, listing a folder name as C<*> will scan every folder that matches. SpamAssassin remembers which mail messages it's learnt already, and will not re-learn those messages again, unless you use the B<--forget> option. Messages learnt as spam will have SpamAssassin markup removed, on the fly. If you make a mistake and scan a mail as ham when it is spam, or vice versa, simply rerun this command with the correct classification, and the mistake will be corrected. SpamAssassin will automatically 'forget' the previous indications. =head1 INTRODUCTION TO BAYESIAN FILTERING (Thanks to Michael Bell for this section!) For a more lengthy description of how this works, go to http://www.paulgraham.com/ and see "A Plan for Spam". It's reasonably readable, even if statistics make me break out in hives. The short semi-inaccurate version: Given training, a spam heuristics engine can take the most "spammy" and "hammy" words and apply probablistic analysis. Furthermore, once given a basis for the analysis, the engine can continue to learn iteratively by applying both it's non-Bayesian and Bayesian ruleset together to create evolving "intelligence". SpamAssassin 2.50 and later supports Bayesian spam analysis, in the form of the BAYES rules. This is a new feature, quite powerful, and is disabled until enough messages have been learnt. The pros of Bayesian spam analysis: =over 4 =item Can greatly reduce false positives and false negatives. It learns from your mail, so it's tailored to your unique e-mail flow. =item Once it starts learning, it can continue to learn from SpamAssassin and improve over time. =back And the cons: =over 4 =item A decent number of messages are required before results are useful for ham/spam determination. =item It's hard to explain why a message is or isn't marked as spam. i.e.: a straightforward rule, that matches, say, "VIAGRA" is easy to understand. If it generates a false positive or false negative, it's fairly easy to understand why. With Bayesian analysis, it's all probabilities - "because the past says it's likely as this falls into a probablistic distribution common to past spam in your systems". Tell that to your users! Tell that to the client when he asks "what can I do to change this". (By the way, the answer in this case is "use whitelisting".) =item It will take disk space and memory. The databases it maintains take quite a lot of resources to store and use. =back =head1 GETTING STARTED Still interested? Ok, here's the guidelines for getting this working. First a high-level overview: =over 4 =item Build a significant sample of both ham and spam. I suggest several thousand of each, placed in SPAM and HAM directories or mailboxes. Yes, you MUST hand-sort this - otherwise the results won't be much better than SpamAssassin on its own. Verify the spamminess/haminess of EVERY message. You're urged to avoid using a publicly available corpus (sample) - this must be taken from YOUR mail server, if it's to be statistically useful. Otherwise, the results may be pretty skewed. =item Use this tool to teach SpamAssassin about these samples, like so: sa-learn --spam /path/to/spam/folder sa-learn --ham /path/to/ham/folder ... Let SpamAssassin proceed, learning stuff. When it finds ham and spam it will add the "interesting tokens" to the database. =item If you need SpamAssassin to forget about specific messages, use the B<--forget> option. This can be applied to either ham or spam that has run through the B processes. It's a bit of a hammer, really, lowering the weighting of the specific tokens in that message (only if that message has been processed before). =item Learning from single messages uses a command like this: cat mailmessage | sa-learn --ham --no-rebuild This is handy for binding to a key in your mail user agent. It's very fast, as all the time-consuming stuff is deferred until you run with the C<--rebuild> option. =item Autolearning is enabled by default If you don't have a corpus of mail saved to learn, you can let SpamAssassin automatically learn the mail that you receive. If you are autolearning from scratch, the amount of mail you receive will determine how long until the BAYES_* rules are activated. =back =head1 EFFECTIVE TRAINING Learning filters require training to be effective. If you don't train them, they won't work. In addition, you need to train them with new messages regularly to keep them up-to-date, or their data will become stale and impact accuracy. You need to train with both spam I ham mails. One type of mail alone will not have any effect. Note that if your mail folders contain things like forwarded spam, discussions of spam-catching rules, etc., this will cause trouble. You should avoid scanning those messages if possible. (An easy way to do this is to move them aside, into a folder which is not scanned.) If the messages you are learning from have already been filtered through SpamAssassin, the learner will compensate for this. In effect, it learns what each message would look like if you had run C over it in advance. Another thing to be aware of, is that typically you should aim to train with at least 1000 messages of spam, and 1000 ham messages, if possible. More is better, but anything over about 5000 messages does not improve accuracy significantly in our tests. Be careful that you train from the same source -- for example, if you train on old spam, but new ham mail, then the classifier will think that a mail with an old date stamp is likely to be spam. It's also worth noting that training with a very small quantity of ham, will produce atrocious results. You should aim to train with at least the same amount (or more if possible!) of ham data than spam. On an on-going basis, it's best to keep training the filter to make sure it has fresh data to work from. There are various ways to do this: =over 4 =item 1. Supervised learning This means keeping a copy of all or most of your mail, separated into spam and ham piles, and periodically re-training using those. It produces the best results, but requires more work from you, the user. (An easy way to do this, by the way, is to create a new folder for 'deleted' messages, and instead of deleting them from other folders, simply move them in there instead. Then keep all spam in a separate folder and never delete it. As long as you remember to move misclassified mails into the correct folder set, it's easy enough to keep up to date.) =item 2. Unsupervised learning from Bayesian classification Another way to train is to chain the results of the Bayesian classifier back into the training, so it reinforces its own decisions. This is only safe if you then retrain it based on any errors you discover. SpamAssassin does not support this method, due to experimental results which strongly indicate that it does not work well, and since Bayes is only one part of the resulting score presented to the user (while Bayes may have made the wrong decision about a mail, it may have been overridden by another system). =item 3. Unsupervised learning from SpamAssassin rules Also called 'auto-learning' in SpamAssassin. Based on statistical analysis of the SpamAssassin success rates, we can automatically train the Bayesian database with a certain degree of confidence that our training data is accurate. It should be supplemented with some supervised training in addition, if possible. This is the default, but can be turned off by setting the SpamAssassin configuration parameter C to 0. =item 4. Mistake-based training This means training on a small number of mails, then only training on messages that SpamAssassin classifies incorrectly. This works, but it takes longer to get it right than a full training session would. =back =head1 OPTIONS =over 4 =item B<--ham> Learn the input message(s) as ham. If you have previously learnt any of the messages as spam, SpamAssassin will forget them first, then re-learn them as ham. Alternatively, if you have previously learnt them as ham, it'll skip them this time around. If the messages have already been filtered through SpamAssassin, the learner will ignore any modifications SpamAssassin may have made. =item B<--spam> Learn the input message(s) as spam. If you have previously learnt any of the messages as ham, SpamAssassin will forget them first, then re-learn them as spam. Alternatively, if you have previously learnt them as spam, it'll skip them this time around. If the messages have already been filtered through SpamAssassin, the learner will ignore any modifications SpamAssassin may have made. =item B<--rebuild> Rebuild the databases, typically done after learning with B<--no-rebuild>, or if you wish to periodically clean the Bayes databases once a day on a busy server. =item B<--force-expire> Forces an expiry attempt, regardless of whether it may be necessary or not. Note: This doesn't mean any tokens will actually expire. Please see the EXPIRATION section below. =item B<--forget> Forget a given message previously learnt. =item B<--dump> I