Spam filter for ASP.NET?

Question

I'm looking for a spam filter that I can integrate into my ASP.NET application. I don't want any delegate services (e.g. Akismet) as I'm doing this for a high traffic website, any suggestions?

Edit: I mean a post spam filter, it's a forum based website.

Edit: Thanks for your answer but I'm not looking for a Captcha, I'm looking for a spam filter, Captcha is not a spam filter it's used for preventing automated spam but it's not a spam filter itself, a spam filter is a piece of software that scans the posts and mark them as spam or not. Actually I already have a Captcha in my application for preventing automated spam.

Answer 1

The technology you're looking for is a CAPTCHA, which stands for: Completely Automated Public Turing test to tell Computers and Humans Apart. It's used to make sure bots don't spam forums and other public posting sites with... well... spam.

For ASP.NET, there are quite a few:

• Jeff Atwood's CodeProject CAPTCHA
• BrainJar's CodeProject CAPTCHA
• ReCAPTCHA for ASP.NET
• BotDetect ASP.NET CAPTCHA
• Mondor's ASP.NET CAPTCHA Control
• And Many, Many More.

Edit: I had taken out the Spam Filter I listed when I edited my answer, putting it back in:

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It looks like someone implemented one here.

By "spam filter" do you mean CAPTCHA? Or Email spam filtering?

Answer 2

If you don't want to use CAPTCHA's, because they annoy people, and you already the site up and running, you could write your own parser to filter out spam. Most spam you see is extremely blatant. Posting hundreds of links in a post. Subject, Body, and Poster name are all exactly the same. Other stuff along those lines. You could write some simple filters, like I did for my blog, to basically cut out 99% of the spam, while your users don't even realize that you are even using filtering.

Answer 3

Although not widely used, since comments/forum posts are typically stored in a database, an insert trigger works remarkably well which looks for certain words in comments and auto triggers a delete. Again, this isn't an ideal solution, but it works for me. There is the possibility of deleting a legit post, but then again, its sometimes near impossible to correctly decipher a captcha...

Answer 4

I use Akismet for spam filtering. There is a .NET interface for available here on CodePlex.

It works very well and the Api is pretty simple. Akismet is free for personal use (making less than $500/month), so I'm not sure about the pricing if you are making some serious money on the website.

Answer 5

I can't recommend this because I've never used it, but I know a small company that had decent luck with A Naive Bayesian Spam Filter for C# by Jason Kester.

I would personally recommend using a 3rd party like Akismet though. Spam filtering is tough business and it is always better to delegate that to someone who can and will keep up with the spammers' techniques over time.

Answer 6

You could check out nBayes, a C# implementation of Paul Graham's plan for spam

Answer 7

hi..even am lookin for a spam filter in my asp application. Did any of the above solutions, especially akismet, work fine for your application? please let me know.

Thanks, Geetha