Despamilator is a plugin based spam detector designed for use on your web forms borne out of two annoyances: Spam being submitted in my web forms and CAPTCHAS being intrusive. Despamilator will apply some commonly used heuristics from the world of anti-spam to help you decide whether your users are human or machine.
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Moved Rails-esque validation gem to the despamilator-rails gem.
Using Despamilator:
require 'despamilator' # some time later... dspam = Despamilator.new('some text with an <h2> tag qthhg') dspam.score #=> the total score for this string (1 is considered high) dspam.matches #=> array of matching filters first_match = dspam.matches.first #=> first matching filter first_match[:filter].name #=> some string with the name of the filter first_match[:filter].description #=> some string to describe first_match[:score] #=> the individual score assigned by this matching filter
As stated, this is a heuristic scanner so its up to the user to decide the thresholds of the scanner. I usually say “it’s spam” if the score reaches 1.
The score will be added to incrementally by each matching filter. So if there is some HTML in there, it will be added to the score. If there is also a script tag of some sort, that will add more.
Each filter decides how much of a score it assigns. For example, detecting a number next to a letter (the numbers_an_words filter) is only a mild hint compared with a script tag (detected by the script_tag filter).
I absolutely welcome new filters and experiments. New filters should be put in the ‘lib/despamilator/filter/’ directory. The core filtering code will detect and use what is in there so you only need to drop the code in. Filters should be simple, no classes etc wrapped around them and should try to perform one simple task. They should always supply the following methods:
* name #=> the name of your filter. * description #=> what your filter will look for. * parse(subject) #=> the method that will be called when parsing. A copy of the message is passed in.
The subject of the detection (including text) is passed into the “parse” method. It provides the following methods…
* text #=> The text of the message. This is immutable but you can alter a duplicate (using "dup"). * register_match! #=> Method that receives the instance of the filter and the assigned score if matched.
Take a look at the “prices” code and tests in “spec/filters/prices.rb”.
This example is to detect the letter “a”. Put the code in lib/despamilator/filter/detect_letter_a.rb:
require 'despamilator/filter_base'
module DespamilatorFilter
class DetectLetterA < Despamilator::Filter
def name
'Detecting the letter A'
end
def description
'Detects the letter "a" in a string for no reason other than a demo'
end
def parse subject
if subject.text.downcase.scan(/a/)
# add 0.1 to the score of the text
subject.register_match!({:score => 0.1, :filter => self})
end
end
end
As previously stated, ensure you put a spec test together as well!
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domainatrix
$ sudo gem install despamilator
Copyright © 2011 Stephen Hardisty
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