PKG-SNF-CS-NIX/SNF_CS_Developer_Package/SNF4SA

               SpamAssassin SNF4SA Plugin for SNFServer

                             README file



              Copyright (C) 2009 ARM Research Labs, LLC.



           See www.armresearch.com for the copyright terms.

                                   

This directory contains the SpamAssassin plugin for SNFServer.



The plugin implements a rule that checks the email message with

SNFServer.



If SNFServer determines that the email message is spam, then the

plugin calculates a plugin score that depends on the SNFServer result.

The plugin score for each SNFServer result is specified in the

configuration file using the "snf_result" configuration line (please

see the INSTALL file for further info).



The GBUdb scan result also changes the plugin score by:



  abs(p * c) ^ 0.5 * sign(p) * MaxWeight



where p is the probability and c is the confidence returned by the

GBUdb scan, sign(p) is -1 if p < 0 and +1 otherwise, and MaxWeight is

specified in the configuration file.  If SNFServer is not configured

to insert the GBUdb scan results into a header in the message, or

MaxWeight is not specified in the configuration file, then the

plugin score is not affected by the GBUdb scan results.



If SpamAssassin supports dynamic score reporting (SpamAssassin version

3.2.0 or later), then the plugin score is added to the score of the

message.



If the version of SpamAssassin is earlier than 3.2.0, then the plugin

behavior is different.  In this case, if the plugin score is equal to

or above a threshold specified in the configuration file, then a fixed

value specified in the configuration file is added to the score of the

message.  If instead the plugin score is below the threshold, then the

score of the message is not changed by this plugin.  The fixed value

is specified by the "score" configuration line, and the threshold is

specified by the "pre_3.2_static_sa_score_threshold" configuration

line.  Please see the INSTALL file for further info.



In addition to scanning the message, the plugin inserts headers into

the email.  The SNFServer must be configured to generate the

X-headers.  Please see the SNFServer documention for configuration

instructions.  The plugin obtains the headers from SNFServer (using

the XCI interface), and inserts the headers into the email message.

The following headers are inserted by the plugin into the message if

SNFServer is configured to generate them:



  1) 'X-SPAM-MessageSniffer-Scan-Result' contains the body of the

  X-MessageSniffer-Scan-Result header inserted by SNFServer.



  2) 'X-SPAM-MessageSniffer-Rules' contains the body of the

  X-MessageSniffer-Rules header inserted by SNFServer.



  3) 'X-SPAM-GBUdb-Analysis' contains the body of the X-GBUdb-Analysis

  header inserted by SNFServer.



Please see the INSTALL file for installation and configuration.