How to Screen Your Blog for Spam

By Amy Lupold Bair

Software that filters the incoming comments in various ways can provide a defense against spammers by identifying and removing comments from your blog that look like spam. These filters give a blogger great tools: They run all hours of the day and they don’t require any effort on your part. But an automated process is never as smart as a human, so you might occasionally lose a valid comment if you use a filtering system.

A third-party software solution called Automattic Akismet is the clear leader when it comes to spam filtering, though many blogging software applications have added their own internal tools, as well. Check to see whether your blog software has any of these technologies in place for you to use; you can probably find some of them available. If you don’t, check to see whether you can add Akismet to your blog.

Keyword filtering

Keyword filters can help you identify incoming comment spam. This kind of filtering is probably the oldest type of protection for blog comments. It might not work all the time because spammers have become much smarter since this technology was first used. Spam filtering usually works by comparing incoming comments against lists of words and/or phrases associated with spam. Matches indicate spam, and the filter yanks those comments.

Keyword filters are typically updated frequently to keep up with the ploys that spammers use. Some of these lists contain web addresses and other computer identification information as well as keywords. Users also can submit and maintain their own lists in case custom spelling or other methods of tricking the antispam system come into use (for example, using V1agra rather than Viagra).

Several services over the years have allowed different blog tools and platforms to take advantage of a central keyword listing. These lists are maintained and updated by a third-party company. Today’s most popular antispam system, Akismet falls into this category.

One problem with this kind of filter system is that some spammers leave nice messages that include bad links. These messages get past the filter because they aren’t offensive and don’t violate any rule that you have.

Blacklists and whitelists

A blog blacklist is a method of keeping spam off your website by preventing certain known spam systems from accessing your comment system or your website as a whole. By specifically identifying spammers from certain addresses, countries, or computers, or by using certain URLs, you can block those individual spammers, keeping your blog much safer.

Most blogging software comes with a blacklist system built in or a system that you can easily add by using a plug-in or third-party solution. Consult your blog software documentation to be sure that you understand how to keep your blacklist up to date and how you can contribute to the blacklist.

Whitelists perform the opposite action of a blacklist by specifically permitting certain visitors or types of visitors. A whitelist is a preselected list of visitors whom you know won’t post spam on your blog. Bloggers use a whitelist in conjunction with a blacklist. Whitelists can allow you to accept comments from visitors who have been misidentified as spammers in the past.

Essentially, you’re making your blog accessible to certain people or computer networks. If you want to guarantee that your mother, for instance, can always post to your blog — or even if you want to set it up so that she doesn’t have to comply with a CAPTCHA or other antispam techniques — add her to the whitelist so that she can post with impunity. Whitelists are uncommon, so if your blogging software doesn’t offer this functionality, you probably can’t find a good third-party solution.

IP banning

Similarly to blacklists, IP banning prevents certain IP addresses or a range of IP networks from accessing your website. IP banning is probably the oldest method of protecting blogs.

An IP (Internet Protocol) address is a series of numbers that identifies a network, a computer, or any networked electronic device within a computer network. Devices such as printers, fax machines, desktop and laptop computers, and some telephones can have their own IP addresses.

Many blog software solutions offer lists of banned IP addresses that they collect from other users of the same software who have identified spammers, and you can automatically update your own list to prevent those spammers from posting to your site.

A potential problem with banning networks or certain IP addresses is that the offending poster may connect via a different IP address the next time that he or she posts something. Banning by IP address can work for known spam companies, but it’s highly fallible because so many computers regularly obtain new IP addresses through their Internet Service Providers (ISPs).

IP banning can also affect people whom you don’t actually want to block. For instance, if you block a computer on a particular network, others who use the same network but are blameless might end up using the offending IP address at some point and be blocked. Many bloggers discount IP banning, saying that it has no real usefulness in today’s mobile world.