Battling Comment Spam

January 31, 2007
coldfusionweb

Fighting comment spam seams like a never ending battle. I've done a lot over the last few years to try and squash it on my blog.

I started out by implementing a list of words that would trigger the comment to be blocked. I found myself updating this list on a weekly basis, never staying on top of it.

I solved that problem by implementing the Bayesian Filter CFC from fusionKit. The bayes filter has worked really well, and produced a suprisingly low number of false positives.

Now just over the weekend I was flodded with a ton of comment spams that were written well enough to get past the bayes filter. They were also all submitted within a few minutes, so there was no time to train my bayes filter.

I'm not a big fan of statically blocking IP addresses, since the owners of IP addresses can change over time. However I think temporary blocks on IP's are OK, so I wrote a little rate limiter that will block IP's that try to post more than 1 comment within a 5 minute time span or IP's that have attempted to post a large number of comments.

I'm sure some of you have probably experienced the same problem, so here you go:

<cfif IsDefined("application.rate_limiter")>
  <cfif StructKeyExists(application.rate_limiter, CGI.REMOTE_ADDR)>
    <cfif application.rate_limiter[CGI.REMOTE_ADDR].attemps GT 1 AND DateDiff("n", application.rate_limiter[CGI.REMOTE_ADDR].last_attempt, Now()) LT 5>
      <p>You are posting too many comments too fast, please slow down and wait 5 min.</p>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].attemps = application.rate_limiter[CGI.REMOTE_ADDR].attemps + 1>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].last_attempt = Now()>
      <cfabort>
    <cfelseif application.rate_limiter[CGI.REMOTE_ADDR].attemps GT 20>
      <p>You have made too many attempts to post a comment. Please try back in a few days.</p>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].attemps = application.rate_limiter[CGI.REMOTE_ADDR].attemps + 1>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].last_attempt = Now()>
      <cfabort>
    <cfelse>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].attemps = application.rate_limiter[CGI.REMOTE_ADDR].attemps + 1>
      <cfset application.rate_limiter[CGI.REMOTE_ADDR].last_attempt = Now()>
    </cfif>
  <cfelse>
    <cfset application.rate_limiter[CGI.REMOTE_ADDR] = StructNew()>
    <cfset application.rate_limiter[CGI.REMOTE_ADDR].attemps = 1>
    <cfset application.rate_limiter[CGI.REMOTE_ADDR].last_attempt = Now()>
  </cfif>
<cfelse>
  <cfset application.rate_limiter = StructNew()>
  <cfset application.rate_limiter[CGI.REMOTE_ADDR] = StructNew()>
  <cfset application.rate_limiter[CGI.REMOTE_ADDR].attemps = 1>
  <cfset application.rate_limiter[CGI.REMOTE_ADDR].last_attempt = Now()>
</cfif>


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Comments

Pete, check out this project from Jake Munson cfformprotect.riaforge.org
Have your tried the CFAkismet CFC? http://devnulled.com/cfakismet We put it on our blog (http://blog.d-p.com) and love it.
@Pete: You might want to adjust the 1 comment per 5 minutes to at least 2 commments. 1 seems a little to strict--especially in the case where someone wants to post an addendum to what they typed.
Hey Dan, Actually it does allow for two comments since it says GT 1 and the attempts are incremented after that point. I wasn't clear about that in my post however. Thanks for pointing that out.
I can understand your code. Could you give me the PHP version please
Great site!e
Good luck with your site in the future!e
Good job, here and there!k
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Thanks for sharing this link, but unfortunately it seems to be offline... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if a staff member here at www.petefreitag.com could post it.

Thanks,
John
Thanks for sharing this link, but unfortunately it seems to be offline... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if a staff member here at www.petefreitag.com could post it.

Thanks,
Mark
Thanks for sharing the link, but unfortunately it seems to be offline... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if a staff member here at www.petefreitag.com could post it.

Thanks,
Alex
Thanks for sharing this link, but unfortunately it seems to be down... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if a staff member here at www.petefreitag.com could post it.

Thanks,
Oliver
Hey,

This is a inquiry for the webmaster/admin here at www.petefreitag.com.

May I use part of the information from your post above if I provide a backlink back to this site?

Thanks,
Jack
Thanks for sharing this link, but unfortunately it seems to be down... Does anybody have a mirror or another source? Please answer to my message if you do!

I would appreciate if someone here at www.petefreitag.com could post it.

Thanks,
Harry
Have you considered the fact that this might work another way? I am wondering if anyone else has come across something
exactly the same in the past? Let me know your thoughts...
Thanks for sharing the link, but argg it seems to be offline... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if someone here at www.petefreitag.com could post it.

Thanks,
Daniel
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Hi,

I have a inquiry for the webmaster/admin here at www.petefreitag.com.

Can I use some of the information from your blog post right above if I provide a link back to your site?

Thanks,
William
Hi,

I have a question for the webmaster/admin here at www.petefreitag.com.

May I use part of the information from your post above if I provide a link back to your site?

Thanks,
John
Hello there,

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Thanks,
Thomas
Greetings,

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Thanks,
Daniel
Hello,

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Thanks,
Oliver
Hello there,

Thanks for sharing this link - but unfortunately it seems to be down? Does anybody here at www.petefreitag.com have a mirror or another source?


Thanks,
Daniel
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Cheers,
Daniel
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Hello there,

This is a inquiry for the webmaster/admin here at www.petefreitag.com.

Can I use part of the information from this post above if I give a link back to this site?

Thanks,
Harry
Hey,

Thanks for sharing this link - but unfortunately it seems to be down? Does anybody here at www.petefreitag.com have a mirror or another source?


Cheers,
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Hello there,

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Cheers,
Jack
I have a blog (Fugitive Seeking Truth) and have had a number of my posts comment-spammed with the same comment that appears several times on this page:

"Thanks for sharing the link - but unfortunately it seems to be down? Does anybody here at [my blog address] have a mirror or another source?" with a name attached.

I also have the comment requesting permission to backlink. Any idea who posts these comments and why?

Thanks,

Blessings and peace,
Ylanne
Hello there,

Thanks for sharing this link - but unfortunately it seems to be not working? Does anybody here at www.petefreitag.com have a mirror or another source?


Cheers,
Peter
Hi! I know this is somewhat off topic but I was wondering if you knew where I could find a captcha plugin for my comment form? I'm using the same blog platform as yours and I'm having trouble finding one? Thanks a lot!
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