In Part 1, we discussed the need for building a regular expression to help us filter spam. I showed how to install and build a regular expression using Regulazy. In this article, we’ll cover testing the regular expression as well as how to add a regular expression to a spam filter.
A Quick Recap
Sticking with what we built in part one (which can be found here ), we’ve found a common theme in the spam we receive with variations on the following subject line – “Viagra is sold here for cheap”.
- V1@gra is sold here for ch3ap
- V!agra 1s sold h3r3 for cheap
- V!@gra sold here for cheap
The final regular expression we built was “^v.{2}gra\ .*?\ sold\ h\w{1}r\w{1}\ for\ ch\w{1}ap$”.
RegexBuilder
After you’ve got a regular expression, you’ll want to test it against possible variations in the spam you receive. You’ll want to grab RegexBuilder. This tool allows you to enter a regular expression and some test text and it will very clearly tell you if your test text would match the expression. RegexBuilder can be found here .
In order to use RegexBuilder, you’ll need to have the Microsoft .NET Framework 2.0 installed – available here .
Testing Regular Expressions using RegexBuilder
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Fire up RegexBuilder
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Copy the regular expression we created into the Regex text field
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Copy each of the tests into the “Text 1” and “Text 2” fields. Click the “+” button to add a “Text 3” field.
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As you type each in, the first three should turn green noting that these three tests match our regular expression. Note that “V!@gra sold here for cheap” doesn’t match out regular expression though. See Figure 1.
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You can keep adding test text to see if other spam variations will match the regular expression.
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In order to fix the expression for the failed test, we can go back to Regulazy or modify the expression in RegexBuilder itself.
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Adding the Regular Expression to your Filter
Each Anti-SPAM application will be different, but most advanced consumer and Enterprise filters will allow for the use of Regular Expressions. One of my top FREE Anti-SPAM tools for home use – Spamihilator (discussed here ) supports Regular Expressions. This section will give you a quick rundown of how to add your newly created RegEx into Spamihilator. Refer to your tool’s user manual to determine if it supports Regex.
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Start Spamihilator. Right click on the Spamihilator icon in your taskbar and select Settings.
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Click on Spam Words
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Click Add…
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Copy your regular expression into the text field and be sure to check the “Regular Expression” checkbox. See Figure 2.
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Click Ok and then Apply.
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That’s it – Spamihilator (or your filter of choosing) will now block our example text.
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This post is part of the series: Free SPAM Filtering using Regular Expressions
This series will walk you through creating a regular expression to filter SPAM as well as walking you through testing the expression and implementing it into a popular FREE Spam filter - Spamihilator.
