Why comment spam still exists - and why I'll stay 'dofollow'

 by Martin Belam, 19 January 2011

If you've been running a blog for any length of time, you'll be sure to have come across the phenomena of comment spam. People pimping sex products and pr0n are easy to spot, but there is a whole breed of spammer out there who are rather more subtle. They particularly target blogs which allow them to post links which aren't marked as 'nofollow', making them valuable in the eyes of search engines.

Why does comment spam still exist?

Well, if you can get a link to your site from a blog with a lot of traffic, there is a chance some of that traffic will click the link and visit you. Link building is also an important search engine optimisation technique. The number of links that point at a site, or indeed an individual page on a site, is one of the factors that search engines use to determine how important a page is, and therefore how highly to rank it.

Won't spam filters catch everything for me?

Ask yourself 'Do spam filters catch everything in your email inbox?' and you'll know the answer. Most blogging platforms come with some form of defence against comment spam, and some systems, like Akismet, work collaboratively across swathes of blogs, but some comment spam is bound to escape the filtering.

Why do some blogs attract more comment spam than others?

Comment spam comes in two main forms - automated spam and hand-crafted spam. The former adopts a scatter-gun approach, attacking the most common blogging platforms, using computers to perform the task. Whether it is one server or a 'bot army' of slave machines, even a very low rate of success is worthwhile given the low effort involved once the spambot is started up.

The hand-crafted spam is harder to deal with. SEO and link-builders trade the addresses of 'dofollow' blogs, where gaining a backlink will aid search engine rankings. You can find hundreds of lists of them with a simple Google search

Rather like the harvesting of virtual gold in World of Warcraft, people are paid a pittance to leave comments on blogs that might add to a site's Google Juice.

Some of the more obvious signs of hand-crafted comment spam are:

  • Including a list of URLs in the comment which are unrelated to your blog's topic
  • A single unrelated URL left dangling at the end of a comment
  • Leaving the full name of a business instead of a real name or nickname, e.g "Hector's Lousiana Realtor"

Some more subtle tell-tale signs:

  • The email address given is a different name to the one left as the commenters name
  • A very short comment including the phrases "nice post", "great post", "great share" or "I subscribed to your blog"
  • Mangled spelling and/or grammar - a symptom of hammering out as many comments as quickly as possible in a foreign tongue.
  • Foreign looking names that are actually keywords. You can use Google Translate or Babelfish to establish whether 'Posaune kaufen' is a name, or the German for 'buy trombone'.

And even harder to spot:

Crafty posts that aim to put related keywords near to their link. For example 'I owe you a debt of gratitude for posting. It has really helped me consolidate my thoughts on the issue' from someone trying to place a link to a debt consolidation agency. Or signing a blog comment 'Alistair conditioning'.

How should you deal with it?

Delete. Delete. Delete. Although sometimes if the comment is actually good, but the link is a bit spammy or NSFW (i.e. a loan shark or dodgy videos) I'll publish the comment but take the link out, and re-label it 'Anonymous'.

So why persist with 'dofollow'?

Inept 'dofollow' comment spam sucks the fun out of blogging, so why do I persist in having 'dofollow' links on my comments? Well, I've been blogging for 8 years now, and still remember that leaving comments on blogs that I admired was a great way of drawing attention to currybetdotnet's early days.

I might be old fashioned, but I fundamentally still believe that 'nofollow' breaks the hyperlink principles of the web, and that people who take the time to contribute a well reasoned comment to my website deserve a link back to their own blog or personal website that 'counts'.

More information and other resources

If you are interested in finding out more, these links may be useful:


One thing that puzzles me about a lot of comment spam is that on the one hand lots of effort goes into pumping out large volumes of spam and quite a lot of thought into sneaky ways to try to make it slip past spam filters and the human eye (as you mention).

But on the other hand... the quality of English is so often so poor and a big give away.

Not that I'm complaining, but I'm surprised it doesn't seem to be worth the spammers' time to go for decent quality English.

Martin, my blog was dofollow for a while and all it did was to attract even more comment spam; I think I still feel the effects today. That slows down the blog for legitimate visitors. Further, even a nofollow link works. I agree that nofollow is broken both in concept and in practice. It is ironic that wikipedia marks all links as nofollow; yet a wikipedia link that survives is among the most legitimate links out there.

Akismet has been a great help.


I applaud your mettle, Martin: few have the tenacity to deal with the volume of spam that a "dofollow" comment blog can generate. (Though the bots are not necessarily that discerning. My own "nofollow" blog receives about 100 spam comments a day - thank god for Askimet!) As someone that, at least for my personal sites (rather than client sites), considers the hoarding of PageRank both artificial and offensive, I wish I could bring myself to open up links on comments, but that would (sadly) make me start to question the motives of my commenters. Perhaps one day.

Regarding Tim's point, it has long been thought that Google still spiders and accords value to Wikipedia links, nofollow'd or no. While that's highly speculative (or at least non-provable), they are indeed among "the most legitimate links" out there, and if I were a search engine in large part based on authority model, that's precisely what I'd do (Google certainly does have a documented history of custom-parsing data that it finds to be important).

I often tweet your posts, but in consideration of the content, I'm giving this one a pass. Sure the, um, less scrupulous of my followers can probably find your blog on one of those lists, but why advertise? ;)

This is really a comment to the talks and presentations article, but it appears that comments are closed.

Any chance of putting up the presentation slides that go with your recent BBC CoJo talk?

You keep referring to the slides, but we can't see them.

Hopefully it's not giving away your secret sauce, since the BBC has already put the video up.

Bravo! I feel that the nofollow attribute does a disservice to the blogosphere. If I am bringing value to someones blog by commenting, why not get a valid (read dofollow) link back to their site? The truth is that by having a dofollow blog you are getting traffic that you would not otherwise get. I read your entire post not because I am a loyal follower but because you have a dofollow blog. Google knows that I came here and knows how long I spent. It ends up being a win-win situation.

As much as I hate blog spammers, I have to object a bit on something.
In principle a comment should not really be used as a mean to get ranking benefits for a linked website. It should be a genuine intent to contribute to the content value.
But if a comment does bring extra value to a blog it may deserve a small reward. Unfortunately linking to a site with a name rather than a keyword DOES hurt certain aspects of the ranking for that particular linked page/site.

I've never noticed those crafty ones on my blog, or should I say never really paid attention. I didn't even realize SEO is affected by dofollow links that have keywords near the link? Either way, thanks for remaining "old school" and keeping a do-follow blog.

I keep my 2 blogs as dofollow much for the same reasons. And really I don't mind people coming for a free link that much, but if they would at least take the time to make it at least seem like they care.

Back when I first started using anti spam plugins, it was kinda disappointing just how popular my blog wasn't. It just takes time, and quality content. Keep it up mate.

Hey Martin! Awesome post. I co-run a tumblr called Blog Comment Spam in which we feature the most bizarre / hilarious / awesome spam comments we find on blogs (our own, or others'). Seeing as you have a lot of experience with spam, would you like to contribute? We'd be honored. Shoot me an e-mail!
- Gina

The comment spam problem is pretty easily solved with a decent filter. I run a DoFollow site to encourage legitimate comments, and check the filter once or twice a week to check if anything decent has been caught. It's (to me at least) no more complicated than that.

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