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Strategies for Preventing Comment Spam

Aug 17, 2007
Bloggers are painfully aware of website owners who try to improve their websites rank by adding links to blogs. There are several strategies for combating this problem. The first and most obvious method is to avoid free blogger sites. These are favorite targets for comment spam.

Bloggers who own their own software can add a no-follow tag. The rel=nofollow tag does not stop the spam, but it does stop robots from following the link. Blogger, owned by Google, implements these tags already. Wordpress has anti-comment spam plug-ins to help bloggers stop comment spam.

Do not bother banning the IP address - unplugging a computer for one hour can change the IP address, and changing a servers IP address is relatively easy. Some companies buy IP addresses in blocks of a hundred or more, and spammers also use open proxies. These are IP addresses that allow anyone access.

Configuring a blog to prevent javascript and HTML code in replies is a solid and easy to implement method of attacking comment spam. It is possible to configure some blog software programs to automatically convert any string that starts with http:// into a url. This will not stop manual comment spams, but it will stop the crawlers.

The spam crawlers search the web looking for descriptive form names. Field names like comment or reply make it too easy for comment spam crawlers to find a potential victim.

Many blogs are using CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart). This new tool requires the user to post a text and number combination before their post is published. However, a simple trip to the freelance bidding forums already indicates that countries (Ukraine and India are the most obvious) are hiring people to do nothing but post comments all day. This undermines CAPTCHA tools anyway!

If you are able to configure your blogs software, then there is a very simple trick for stop automated comment spam software. The form submit HTML is:

form method="post" action="http://www.example.com/bin/comment"

The action specifies the web address (URL) of the executable used to publish the form results. Simply remove it and add an onsubmit attribute:

form method="post"
onsubmit="this.action=http://www.example.com/+bin/post-a-comment"

This is not 100% effective, but it will stop most spam crawlers.

There are two other methods that are available to most bloggers. The first is user authentication - this requires the person to sign up for a user name and password before publishing a post. This slows down comment spammers in two ways: (1) they must take an extra step before publishing, and (2) most authentication programs are configured to accept an email address once.

The second method is to moderate every post before it is published, but the sheer time involved can be daunting. However, the advantages of having 100% control over your blogs content can tip the scales in the favor of moderating. Many posts do not use relative keywords, or post irrelevant comments based on an emotional reaction to the information. Moderating the blog allows the blog owner total control over the information on their page.
About the Author
The Commentator is a unique program that blocks comment spam, while it builds a double opt in mailing list. For more information visit
The Commentator
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