Spammers Find a Weakness in Mollom

Posted by Hans de Ruiter

Logging in to work on this website today, I was greeted by an ugly sight: comment spam! The number of comments on this website had increased by over 150. It appears that spammers have found a weakness in Mollom, and exploited it.

Mollom blocks spam by analysing comments, and then grading it as "ham" (i.e., a genuine comment), "spam," and "unsure." If it is unsure of whether the comment is spam or not, then the submitter is presented with a captcha image, and must enter the characters shown. These images are only readable by humans, at least no-one has shown a spambot that can interpret them so far. If the user enters the captcha characters correctly, then the comment is accepted as ham, otherwise it is rejected as spam.

The spam that made it through has such innocuous content such as "great site," or "Thanks for this." This is made to look like a genuine comment. What makes it spam, is that the comment's "author" is something like "enlarge_your_..." (I leave ... to your imagination, it's not hard to guess), or the name of a certain product. Plus, the "author's" website is the website belonging to the spammer, who almost always trying to sell shady/dirty products and services.

The number of spam attempts that this website receives rose sharply at the end of September from 20-40 per day up to hundreds per day (peaking at 484 spam attempts on 1 October). Up till now almost all of them were blocked. It has just been over the last day or so that they have broken through. Needless to say, I will be monitoring the situation, and contacting Mollom if it continues.

Comments (0) | 24 October 2009