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Encyclopedia > SpamAssassin
SpamAssassin
Developer: The SpamAssassin team
Latest release: 3.2.3 / August 9, 2007
OS: Cross-platform
Genre: Email spam filter
License: Apache License 2.0
Website: spamassassin.apache.org

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. Image File history File links This is a lossless scalable vector image. ... Image File history File links Size of this preview: 800 × 340 pixelsFull resolution (2384 × 1014 pixel, file size: 132 KB, MIME type: image/png) The SpamAssassin Logo, from the Apache Software Foundation : Our logo is by Christian Rauh, and was the result of an extensive LogoContest. ... “Software development” redirects here. ... A software release is the distribution, whether public or private, of an initial or new and upgraded version of a computer software product. ... is the 221st day of the year (222nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... // An operating system (OS) is the software that manages the sharing of the resources of a computer. ... A cross-platform (or platform independent) programming language, software application or hardware device works on more than one system platform (e. ... Computer software can be organized into categories based on common function, type, or field of use. ... A mail filter is a piece of software which takes an input of an email message. ... A software license is a legal agreement which may take the form of a proprietary or gratuitous license as well as a memorandum of contract between a producer and a user of computer software. ... The Apache License (Apache Software License previous to version 2. ... A website (alternatively, Web site or web site) is a collection of Web pages, images, videos and other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet, cell phone or a LAN. A Web page is a document, typically written in HTML... A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... The Apache License (Apache Software License previous to version 2. ... E-mail spam, also known as bulk e-mail or junk e-mail is a subset of spam that involves sending nearly identical messages to numerous recipients by e-mail. ... To prevent e-mail spam, both end users and administrators of e-mail systems use various anti-spam techniques. ... It has been suggested that this article be split into multiple articles. ...


SpamAssassin is generally regarded as one of the most effective spam filters, especially when used in combination with spam databases. 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. For instance, graphic-only spam messages have no text to compare to therefore checking the sender's originating mailserver 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.

Contents

History

SpamAssassin was created by Justin Mason who had maintained a number of patches against an earlier program named filter.plx by Mark Jeftovic, which in turn was begun in August 1997. Mason rewrote all of Jeftovic's code from scratch and uploaded the resulting codebase to SourceForge.net on April 20, 2001. For the band, see 1997 (band). ... SourceForge is a collaborative revision control and software development management system. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ...


Methods of usage

SpamAssassin is a Perl-based application (Mail::SpamAssassin in CPAN) which is usually used to filter all incoming mail for one or several users. It can be run as a standalone application or as a client (spamc) that communicates with a daemon (spamd). The latter mode of operation has performance benefits, but under certain circumstances may introduce additional security risks. Wikibooks has a book on the topic of Perl Programming Perl is a dynamic programming language created by Larry Wall and first released in 1987. ... CPAN is an acronym standing for Comprehensive Perl Archive Network. ... Stand-alone is a confusing and misleading term, used to refer to various categories of computer programs, but rarely in a consistent fashion. ... In computing, a client is a system that accesses a (remote) service on another computer by some kind of network. ... In Unix and other computer multitasking operating systems, a daemon is a computer program that runs in the background, rather than under the direct control of a user; they are usually instantiated as processes. ...


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. Mail filter programs such as procmail can be made to pipe all incoming mail through SpamAssassin with an adjustment to user's .procmailrc file. A mail filter is a piece of software which takes an input of an e-mail message. ... An email client (or mail user agent [MUA]) is a computer program that is used to read and send email. ... Procmail is a mail delivery agent (MDA) or mail filter, a program to process incoming emails on a computer, widely used on Unix systems. ... A pipe is an operating system mechanism originating in Unix, which allows the user to direct the output of one shell command through another command. ...


Anti-spam techniques

SpamAssassin comes with a large set of rules which are applied to determine whether an email is spam or not. 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. 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. In computing, a regular expression is a string that is used to describe or match a set of strings, according to certain syntax rules. ...


Each test has a label and a description. 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". 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. 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. 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".

E-mail recognized as spam by SpamAssassin, here in the Novell Evolution email client.

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. 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. 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. Spam mail recognized by SpamAssassin This is a screenshot of copyrighted computer software. ... Spam mail recognized by SpamAssassin This is a screenshot of copyrighted computer software. ... Evolution or Novell Evolution (formerly Ximian Evolution, prior to Novells 2003 acquisition of Ximian) is the official personal information manager and workgroup information management tool for GNOME. It combines e-mail, calendar, address book, and task list management functions. ... Look up mime in Wiktionary, the free dictionary. ...


The user can customize these filters using a file "user_prefs" in their home directory. Within this file, they can specify individuals whose emails are never considered spam, or change the scores for certain rules. 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. This can be very useful to users receiving a lot of foreign spam but never actually corresponding with people in that language. In computing, a home directory is a directory which contains the personal files of a particular user of the system. ...


Network-based filtering methods

SpamAssassin also supports:

as a means to tell 'ham' from 'spam'. A DNS Blacklist, or DNSBL (definition below), is a means by which an Internet site may publish a list of IP addresses that some people may want to avoid and in a format which can be easily queried by computer programs on the Internet. ... SURBL is an acronym for Spam URI Realtime Blocklists, a method for detecting spam by searching e-mail message bodies for Uniform Resource Identifiers (URIs) which are known to appear in spam messages. ... Distributed Checksum Clearinghouse (also referred to as DCC), is a hash sharing method of spam email detection. ... Vipuls Razor is a checksum based distributed, collaborative, spam detection and filtering network. ... Hashcash is a proof-of-work system designed to limit email spam and denial of service attacks. ... In computing, Sender Policy Framework (SPF) is an extension to the Simple Mail Transfer Protocol (SMTP). ...


More methods can be added reasonably easily by writing a Perl plug-in for SpamAssassin.


Bayesian filtering

SpamAssassin by default tries to reinforce its own rules through Bayesian filtering, but Bayesian learning is most effective with actual user input. Typically, the user is expected to "feed" example spam mails and example "ham" (useful) mails to the filter, which can then learn the difference between the two. For this purpose, SpamAssassin provides the command-line tool sa-learn, which can be instructed to learn a single mail or an entire mailbox as either ham or spam. Bayesian spam filtering (pronounced Bays-ee-en, IPA pronunciation: , after Rev. ...


Typically, the user will move unrecognized spam to a separate folder for a while, and then run sa-learn on the folder of non-spam and on the folder of spam separately. Alternatively, if the mail user agent supports it, sa-learn can be called for individual emails. Regardless of the method used to perform the learning, SpamAssassin's Bayesian test will subsequently assign a higher score to e-mails that are similar to previously received spam (or, more precisely, to those emails that are different from non-spam in ways similar to previously received spam e-mails).


Licensing

SpamAssassin is free/open source software, licensed under the Apache License 2.0. Versions prior to 3.0 are dual-licensed under the Artistic License and the GNU General Public License. This article is about free software as used in the sociopolitical free software movement; for non-free software distributed without charge, see freeware. ... ... The Apache License (Apache Software License previous to version 2. ... The Artistic License is a software license used for certain free software packages, most notably the standard Perl implementation, most of CPAN modules and Parrot, which are dual-licensed under the Artistic License and the GNU General Public License (GPL). ... The GNU logo The GNU General Public License (GNU GPL or simply GPL) is a widely-used free software license, originally written by Richard Stallman for the GNU project. ...


sa-compile

sa-compile is a utility distributed with SpamAssassin as of version 3.2.0. It compiles a SpamAssassin ruleset into a deterministic finite automaton that allows SpamAssassin to use processor power more efficiently. In the theory of computation, a deterministic finite state machine or deterministic finite automaton (DFA) is a finite state machine where for each pair of state and input symbol there is a deterministic next state. ...


Testing SpamAssassin

Most implementations of SpamAssassin will trigger on the GTUBE, a 68 byte string not unlike the antivirus EICAR test file. If this string is inserted in a RFC 2822 formatted message and passed through the SpamAssassin engine, SpamAssassin will trigger with a weight of 1000. The GTUBE (Generic Test for Unsolicited Bulk Email) is a test string used to test anti spam solutions, notably those based on spamassassin. ... The Eicar test file is a file, developed by the EICAR organization, that is used in testing anti-virus scanners for their integrity in detecting viruses. ...


See also

Free software Portal

The following free/open source applications have support for SpamAssassin: Image File history File links Free_Software_Portal_Logo. ...

  • Citadel - email/groupware server contains built-in support for SpamAssassin integration
  • MailScanner - "A Free Anti-Virus and Anti-Spam Filter"
  • KMail supports SpamAssassin and other spam filters, through some modular filters.
  • MIMEDefang
  • SmarterMail 4.x - Free edition

SpamAssassin has also been used in many commercial products including: More screenshots on the project site // What is Citadel? Citadel (formerly Citadel/UX) is an open source groupware (messaging and collaboration) software package, written to run on open source operating systems such as Linux or BSD. It is designed to be a messaging platform that you can build a community... MailScanner is an open-source E-mail program to secure against spam and viruses. ... KMail is the email client of the KDE Desktop Environment. ... MIMEDefang is a GPL licenced framework for filtering e-mail. ...

  • Atmail uses the Spamassassin engine, includes custom rulesets, filters and Web interface for users to modify SA runtime preferences
  • AntibodyMX incorporates SpamAssassin
  • McAfee uses SpamAssassin in its anti-spam tool SpamKiller
  • Spamnix is also based on SpamAssassin
  • Kerio MailServer uses SpamEliminator, which is based on SpamAssassin, for heuristic spam filtering
  • MailLaunder is a hosted spam and virus solution that uses SpamAssassin as part of the filtering process
  • SmarterMail Enterprise - Enterprise version
  • MailLaunder is a hosted spam and virus solution that uses SpamAssassin as part of the filtering process
  • Mail Them Pro is a mailer which has built-in Spamassassin and allows to check email before mailing with Spamassassin to prevent email being considered as a spam
  • SpamMinder is a mail gateway service which transparently filters spam from messages passed through it, using SpamAssassin.

Other free/open-source applications that have the same goal: @Mail is a commercial open source WebMail, Mail-Server and Groupware solution designed by Calacode, location in Sydney, Australia. ... McAfee, Inc. ... Kerio MailServer is secure mail server developed by Kerio Technologies. ...

Categories: Possible copyright violations ... CRM114 (full name: The CRM114 Discriminator) is a program based upon a statistical approach for classifying data, and especially used for filtering email spam. ...

External links


  Results from FactBites:
 
SpamAssassin - Wikipedia, the free encyclopedia (980 words)
SpamAssassin is generally regarded as one of the most effective spam filters, especially when used in combination with spam databases.
SpamAssassin was created by Justin Mason who had maintained a number of patches against an earlier program named filter.plx by Mark Jeftovic, which in turn was begun in August 1997.
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.
  More results at FactBites »

 
 

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