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The Message Sniffer Antispam Plugin for SpamAssassin significantly improves the performance of SpamAssassin installations by providing a range of advanced features that improve both accuracy and speed without additional tuning.
- Add or subtract weight to SpamAssassin scores based on scan result codes.
- Add or subtract weight to SpamAssassin scores based on realtime IP reputation statistics.
- Optionally short-circuit other SpamAssassin tests based on scan result codes.
- Inject Message Sniffer headers for later analysis and easy debugging.
How Do I Get Started?
- Get a 30 Day Free Trial (or use your current SNF license inormation).
- Install SNFServer for your platform. (see Products page).
- Download the SNF4SA from the Products page.
- Follow the INSTALL instructions included in the distribution.
SNF4SA - Antispam Plugin For SpamAssassin INSTALL
SpamAssassin SNF4SA Plugin for SNFServer Installation and Configuration Copyright (C) 2009 ARM Research Labs, LLC. See www.armresearch.com for the copyright terms. Installing SpamAssassin SNF4SA plugin for SNFServer involves the following steps: 1) Copy snf4sa.pm and snf4sa.cf to /etc/mail/spamassassin . 2) Edit /etc/mail/spamassassin/snf4sa.cf plugin configuration file to meet your needs. See below for a description of the configuration settings. The module writes the email message to a temporary file in /tmp/snf4sa. If this directory doesn't exist, the script creates it with permission 777. This allows both the script and SNFServer to write to that directory. If that directory already exists, ensure that it has a permission of 777. The plugin uses the SNFServer results to calculate a plugin score. For SpamAssassin with a version of 3.2.0 or later, this plugin score is added to the SpamAssassin score for the message. If the SpamAssassin version is earlier than 3.2.0, then the plugin compares the plugin score to plugin score threshold. If the plugin score is greater than or equal to the plugin score threshold, then a static score is added to the SpamAssassin score for the message. Both the plugin score threshold and static score are specified in the configuration file. Plugin Configuration Settings ----------------------------- The plugin file (snf4sa.cf) contains required lines that: 1) Configures SpamAssassin to load the plugin. 2) Describes the plugin. 3) Configures SpamAssassin to add the X-Spam-SNF-Result header to the email. This header contains the results of the SNF scan. In addition, there are lines that can be configured by the user that specifies: 1) Which emails to process through SNFServer. 2) The relationship between SNFServer results and the plugin score. You can specify the value added to or subtracted from the SpamAssasin score for each SNFServer result. You can also specify whether SpamAssasin should abort further processing for eacn SNFServer result. 3) The relationship between the GBUdb results and the plugin score. The GBUdb probability p and confidence c add the following value to the SpamAssasin score: abs(p * c) ^ 0.5 * sign(p) * MaxWeight where sign(p) is -1 if p < 0, and +1 otherwise, and MaxWeight is specified in a configuration line. MaxWeight is greater than or equal to zero. If MaxWeight isn't specified in the configuration file, then the GBUdb results don't affect the plugin score. 4) The plugin score threshold and static score (used only if the SpamAssassin version is earlier than 3.2.0). To specify which emails to process, use a line similar to: full SNF4SA eval:snf4sa_sacheck() The above line specifies that all emails be processed. Please see the SpamAssassin documentation for other options. To specify the relationship between the SNFServer results and the plugin score, enter zero or more lines with the format: snf_result NN sa_score S short_circuit_[yes|no] where NN specifies the SNFServer result, and S is the plugin score for that SNFServer result. [yes|no] is "yes" if further scanning should be skipped if SNFServer returns the result specified by NN, or "no" if further scanning should not be skipped. NN can be a combination of a series of one or more integers, and a range of integers specified by N-M, where N and M are integers. The "short_circuit_[yes|no]" is optional, and the default value for [yes|no] is "no" (which specifies that SpamAssasin continue scanning). NOTE: There must not be any space when specifying a range of integers. For example, specify "34-43" rather than the incorrect "34 - 43". For example: snf_result 63 sa_score 2.5 short_circuit_no causes the plugin to add 2.5 to the plugin score if SNFServer returns 63 (which in the default SNFServer configuration corresponds to "caution"). Another example: snf_result 45 47-62 sa_score 5.0 short_circuit_yes causes the plugin to add 5.0 to the plugin score and stop further processing if SNFServer returns 45 or 47 thru 62. Final example: snf_result 1 sa_score -5.0 causes the plugin to subtract 5.0 from the plugin score. SpamAssassin continues to process the email. If SNFServer returns a result that isn't specified, then the plugin adds zero to the plugin score. The following line specifies the MaxWeight parameter: GBUdb_max_weight MaxWeight where MaxWeight is the value to specified. For example, GBUdb_max_weight 3.0 specifies a MaxWeight value of 3.0. For SpamAssassin with version earlier than 3.2.0 ------------------------------------------------ The following line specifies the plugin score threshold: pre_3.2_plugin_score_threshold Threshold where Threshold is the value to specified. For example: pre_3.2_plugin_score_threshold 1.1 causes the static score to be added if the plugin score is equal to or greater than 1.1. The following line specifies the static score: score SNF4SA Score where Score is the static score to add to the SpamAssassin score for the message. For example: score SNF4SA 8.0 specifies a static score of 8.0. If the SpamAssassin version is earlier than 3.2.0, and the plugin score is equal to or greater than the plugin score threshold, then a value of 8.0 would be added to the SpamAssassin score for the message. Debugging the configuration --------------------------- The configuration can be tested by running spamassassin --lint This outputs a message if any line in in the configuration file cannot be parsed, along with the offending line. In order to obtain more detailed information, run spamassassin -D --lint This command outputs information about why a line could not be parsed. The output includes a great deal of other debugging information; you can filter the information relevant to this plugin like this: spamassassin -D --lint 2>&1 | grep snf4sa