![]() ![]() SpamAssassin by default tries to reinforce its own rules through Bayesian filtering, but Bayesian learning is most effective with actual user input. More methods can be added reasonably easily by writing a Perl plug-in for SpamAssassin. checksum-based filters such as the Distributed Checksum Clearinghouses, Vipul's Razor and the Cloudmark Authority plug-in (commercial).URI blacklists such as SURBL or which track spam websites.This can be very useful to users receiving a lot of foreign spam but never actually corresponding with people in that language. The user can also define a list of languages which they want to receive mail in, and SpamAssassin then assigns a higher score to all mails that appear to be written in another language. Within this file, they can specify individuals whose emails are never considered spam, or change the scores for certain rules. ![]() The user can customize these filters using a file "user_prefs" in their home directory. If the score is lower than the defined settings, by default the information about the passed tests and total score is still added to the email headers and can be used in post-processing for less severe actions, such as tagging the mail as suspicious. In the default configuration, the content of the mail is appended as a MIME attachment, with a brief excerpt in the message body, and a description of the tests which resulted in the mail being classified as spam. When a mail's total score is higher than the "required_score" setting in SpamAssassin's configuration, the mail is treated as spam and rewritten according to several options. On the other hand, some tests, such as those for invalid message IDs or years, result in a very high score being assigned, where even a single test can almost put a mail "over the edge". With a spam threshold of 5 (default as of SpamAssassin version 2.55), several other tests would usually have to fail for the mail to be classified as spam. A mail that fails that test (in this case, contains certain variants of the "limited time only" phrase) might be assigned a score of +0.3. The label is usually an all upper case identifier separated with underscores, such as "LIMITED_TIME_ONLY", with the description for that label being "Offers a limited time offer". The total score resulting from all tests or other criteria can then be used by the end user or by the ISP to set the conditions under which email is moved to a separate spam folder, deleted, flagged etc.Įach test has a label and a description. To decide, specific fields within the email header and the email body are typically searched for certain regular expressions, and if these expressions match, the email is assigned a certain score, depending on the test, and several (customizable) headers are added to the mail. SpamAssassin (usually hosted on Linux servers) comes with a large set of rules which are applied to determine whether an email is spam or not. Mail filter programs such as procmail can be made to pipe all incoming mail through SpamAssassin with an adjustment to user's. Typically either variant of the application is set up in a generic mail filter program, or it is called directly from a mail user agent that supports this, whenever new mail arrives. The latter mode of operation has performance benefits, but under certain circumstances may introduce additional security risks. It can be run as a standalone application or as a client ( spamc) that communicates with a daemon ( spamd). SpamAssassin is a Perl-based application ( Mail::SpamAssassin in CPAN) which is usually used to filter all incoming mail for one or several users. Mason rewrote all of Jeftovic's code from scratch and uploaded the resulting codebase to on April 20, 2001. SpamAssassin was created by Justin Mason who had maintained a number of patches against an earlier program named x by Mark Jeftovic, which in turn was begun in August 1997. For instance, graphic-only spam messages have no text to compare to therefore checking the sender's originating hosting mail server and included links against various databases of known e-mail abusers enables the prevention of unnecessary or non-personal mail getting through to the end user. While simple text-matching alone may, for most users, be sufficient to correctly classify a majority of incoming mail the complexity involved in the combination of the comparison of words and symbols used in conjunction with the sources of spam may far exceed the average user's capability. SpamAssassin is generally regarded as one of the most effective spam filters, especially when used in combination with spam databases. SpamAssassin is a computer program released under the Apache License 2.0 used for e-mail spam filtering based on content-matching rules, which also supports DNS-based, checksum-based and statistical filtering, supported by external programs and online databases.
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