on Google’s Webmaster Central Blog warns comment spam can contain “disturbing” images and content, which can put off consumers and other readers.

How does comment spam work?

Comment spam works because search engines such as Google place a high value on inbound links. If I want to help my website climb the rankings and I do not care how I do it, I can set up a robot to race around the web, leaving gibberish comments and linking to my site. I am therefore a link-juice thieving fiend.
However, Google is wise to this and a number of years ago created the nofollow tag, which gave webmasters the power to withhold such perks from robots.
Unfortunately, within many sectors (search in particular!) individuals spend valuable time participating in online debate and enriching the industry through their comments – surely they deserve the link juice? 
So what other ways of beating the spammers exist?

Here are a few of the most commonly-used solutions, feel free to post and let me know if they have worked for you or not. Just as spammers destroyed the usefulness of email marketing, comment spammers threaten the vibrant online community and the usefulness of participating in it.
Don’t call your comment form ‘comment form’

Many of the bots dancing round the WWW, littering it with spam are attracted to certain words. Being a little more creative in what you name the comments section will not put off the more sophisticated spammers but may put off some.
Moderate your comments

It is a time-consuming pain, but this is the one failsafe way of preventing comment spam. If you personally approve each comment made to text, you will obviously not approve rubbish. This might be viable for a small business blog but for popular posts, it will be a time consuming nightmare. Also, it can really stifle the pace of debate.
Filter your comments

Just like your email decides which messages are not genuine, it is possible to invest in software which attempts to determine which comments are from real people and which are not. Like most technology-based things, there is no quick fix. Spammers get more clever and you have to make sure your anti-spam weapons can keep up.

A CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart) is usually a piece of obfuscated text a machine would find it hard to read, which ensures only human beings can leave comments. These can cause accessibility issues for your site, because they effectively stop people with sight disabilities who are using a screen reader from taking part in the debate.
Block multiple posts

Webmasters can block suspicious behaviour by limiting the number of posts a visitor can make within a certain time, meaning a spambot could not fill your entire blog with nonsense. Unfortunately, it can be difficult to decide what settings to use in order to avoid stopping highly active commentators from taking part in the debate.

Kevin Gibbons is Director of Search at