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You may find some tests more indicative of spam than SpamAssassin does by default. If SpamAssassin already provides a test that you value but doesn't assign it a high enough score (higher scores are more indicative of spam), you can easily modify the score of the test. Similarly, if one of SpamAssassin's tests is giving you too many false positives, you can reduce its score or disable the test entirely by setting its score to 0. SpamAssassin will not attempt to run a test with a score of 0.
3.2.1 Modifying Scores Systemwide
Make systemwide score adjustments in the systemwide configuration file, typically /etc/mail/spamassassin/local.cf . To modify the score of a test, you must first determine its test name , either by reading the ruleset files or by examining the spam report from a message. To get a spam report on a message that doesn't score high enough for SpamAssassin to generate a report, you can use spamassassin --test-mode , as described in Chapter 2.
To change the score of a test, simply add a new score directive to the configuration file, like this:
score HTML_WIN_OPEN 2
This will enable the HTML_WIN_OPEN test and add two points to the score of messages that test positive on this test.
You can use the same approach to modify the descriptions of tests by adding new describe directives. For example, the default description for the HOT_NASTY test is "Possible porn - Hot, Nasty, Wild, Young". To shorten that to "Possible porn", add this directive to the configuration file:
describe HOT_NASTY Possible porn
3.2.2 Modifying Scores on a Per- User Basis
Users can use the score directive in per-user preference files to change the scoring of a test for an individual user. To do so, a user edits the .spamassassin/user_prefs file in her home directory and adds score directives. This approach to customizing scores is the simplest, but it requires users to have accounts on the system and access to files in their accounts.
3.2.3 Storing Scores in an SQL Database
When users do not have accounts or shell access (e.g., on a system that is an IMAP or webmail server), per-user scores can be stored in an SQL database and spamd can be configured to look up scores in the database. To store scores in SQL, you must install the DBI Perl module and an appropriate driver module for your SQL database server. Common choices are DBD-mysql (for the MySQL server), DBD-Pg (for the PostgreSQL server), and DBD-ODBC (for connection to an ODBC-compliant server). 
You should create a database and a user with privileges to access it. You must then create a table in the database to store the user scores. The SpamAssassin source code includes a schema for a MySQL table in the sql subdirectory, which is shown in Example 3-2. SpamAssassin 3.0 also includes a schema for a PostgreSQL table.
Example 3-2. A MySQL table for user scores
CREATE TABLE userpref ( username varchar(100) NOT NULL, preference varchar(30) NOT NULL, value varchar(100) NOT NULL, prefid int(11) NOT NULL auto_increment, PRIMARY KEY (prefid), INDEX (username) ) TYPE=MyISAM;
You can use a different name for the table. The name given in Example 3-2 is the default, however, and using it will require the least amount of SpamAssassin configuration effort.
Each row in this table specifies the score for a single test for an individual user. SpamAssassin expects the columns to contain the following information:
The prefid column and the PRIMARY KEY and INDEX clauses are useful but not necessary. prefid defines a primary key for the table, and an index is built on the username column to speed up queries.
To configure SQL support for user scores, set the following configuration parameters in your systemwide configuration file ( local.cf ):
Finally, you'll need to start spamd with the --nouser-config command-line option and either the --sql-config or --setuid-with-sql option to enable SQL-based configuration (and disable the use of ~/.spamassassin/user_prefs files, which cannot be used by spamd together with SQL). If spamd runs as a non- root user, or if your users don't have home directories, use --sql-config ; if spamd runs as root and users have home directories, using --setuid-with-sql will enable spamd 's usual practice of changing uid to the user running spamc so that it can access the user's autowhitelist files.
3.2.4 Storing Scores in an LDAP Database
Another way to store per-user preferences in SpamAssassin 3.0 is in an LDAP (Lightweight Directory Access Protocol) database. This approach may appeal particularly to sites that already store their user account configuration in LDAP. To store scores in LDAP, you must install the Net::LDAP and URI Perl modules.
LDAP objects (like those that represent users) and their attributes (such as username, password, email address, etc.) are defined by one or more LDAP schemas . To add SpamAssassin preferences to your users, extend the objectClass that represents a user to allow an additional, optional spamassassin attribute, which you should define like this:
# spamassassin # see http://SpamAssassin.org/ . attributetype ( 2.16.840.1.1137126.96.36.199 NAME 'spamassassin' DESC 'SpamAssassin user preferences settings' EQUALITY caseExactMatch SYNTAX 188.8.131.52.4.1.14184.108.40.206.15 )
The attribute SYNTAX must be multivalued (as in the example, which specifies the DirectoryString syntax with object identifier (OID) 220.127.116.11.4.1.1418.104.22.168.15), because a user object will have multiple spamassassin attributes, one for each preference setting.
The attributes themselves should be stored in the database. A spamassassin LDAP attribute should be set to the name of a SpamAssassin configuration directive followed by the value for the directive, separated by a space. SpamAssassin 3.0 includes an example of what such user definitions might look like in LDIF (LDAP Interchange Format) format. The spamassassin attribute added to this user's LDAP entry is emphasized :
dn: cn=Curley Anderson,ou=MemberGroupB,o=stooges ou: MemberGroupB o: stooges cn: Curley Anderson objectClass: top objectClass: person objectClass: organizationalPerson objectClass: inetOrgPerson mail: CAnderson@isp.com givenname: Curley sn: Anderson uid: curley initials: Joe homePostalAddress: 14 Cherry Ln.$Plano TX 78888 postalAddress: 15 Fitzhugh Ave. spamassassin: add_header all Foo LDAP read l: Dallas st: TX postalcode: 76888 pager: 800-555-1319 homePhone: 800-555-1313 telephoneNumber: (800)555-1214 mobile: 800-555-1318 title: Developemnt Engineer facsimileTelephoneNumber: 800-555-3318 userPassword: curleysecret
To configure LDAP support for user scores, set the following configuration parameters in your systemwide configuration file ( local.cf ):
Finally, you'll need to start spamd with the --nouser-config command-line option and either the --ldap-config or --setuid-with-ldap option to enable LDAP-based configuration (and disable the use of ~/.spamassassin/user_prefs files, which cannot be used by spamd together with LDAP). If spamd runs as a non- root user, or if your users don't have home directories, use --ldap-config ; if spamd runs as root and users have home directories, using --setuid-with-ldap will enable spamd 's usual practice of changing uid to the user running spamc so that it can access the user's autowhitelist files.
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