SpamFilter - URL Filtering
Overview
SpamFilter has the ability to filter emails based on URLs contained within the body of the message. If a URL within the message falls into a particular category, the Spam score of that message will be increased, thereby increasing the probability of the message getting caught as Spam. By default, only a few categories have been enabled for scoring.
Description
To put this feature into context consider the following example. A message is sent to you which contains a URL to a malware distribution site. The eSoft URL database has the site categorized in the Spyware and Malicious Sites category.
When the message comes in, SpamFilter will check the URL against the eSoft database and see that the URL contained in the message is a Spyware or Malicious site. SpamFilter will then add a score of 8 (by default) to the message.
In most cases this will cause the message to be quarantined or rejected, preventing the message from being delivered and the URL from being accessed. This is a very powerful technique to not only prevent Spam, but to increase security of your network. This scoring can be applied for any of the 53 URL categories currently supported by eSoft.
Configuration
By default, this functionality will be enabled for the Security categories. These are Spyware and Malicious Sites, Spam, and Compromised. Additionally, the Drugs and Pornography categories will also receive an increased Spam score.
To add categories to this list you must use custom Spam scores. Go to the SpamFilter menu and click Settings. Click on the Scores button to access the Spam Score configuration page. In most situations the setting will be set to Default. Change the option to Custom to reveal the various rules used by the SpamFilter to score message. To change the URL categories choose eSoft URL Categories from the group drop down list.
After selecting this you can see you have the option to enter or change the score for any category. Placing your mouse cursor over the category will give a brief description at the bottom of the page. A positive score will increase the chance that a message is caught as Spam, while a negative score will decrease the likelihood that it is Spam.
As an example, let's assume some users have been getting Spam containing links to sites containing nudity. To increase the chance that these are caught we would find the nudity category, listed as E_URL_CAT_NUDITY, and enter a score. Then, click Apply to save your changes.
Troubleshooting
Use conservative scores when enabling this feature as it could cause Bayesian or Historical Averaging databases to incorrectly score future messages. It is not recommended to use anything over 17, the default high threshold under most circumstances.
To find the categorization for any URL browse to our Test a Site page. This will show the current eSoft categorization and allow you to make suggestions.
