Google's Comment Spam Prevention Method | January 21, 2005

As I’m sure most of you are aware, Google have introduced a means of preventing comment spammers getting any search ranking benefit from your site. Google works by assigning every page in it’s index a value known as a Page Rank (after co-founder Larry Page). Page Rank (or PR) is essentially a measure of a sites popularity and is worked out based on the PR of the other sites linking to that site. Because blogs tend to have lots of incoming links, they often attract a high PR and are a prime target for unscrupulous site owners intent on increasing their own sites visibility. By adding comments on high PR sites with links back to their own site, they hope to give the target site a PR boost.

To counter this Google are making use of the rel attribute. By adding rel="nofollow" to your outbound links you’re telling Google not to count your vote towards the sites final PR. Most of the better known blog publishing organisations have already released plugins for their applications to automatically add this attribute to sites left in comments., and more will follow.

Site owners hope this will go some way to help prevent comment spam. It seems logical to assume that if the benefits are taken away, people will stop, and for casual comment spammers it probably will. However the vast amount of comment spam–like regular spam–is automated so it’s possible that as effectiveness decreases the amount of automated comment spam may actually increase.

As well as stopping spammers, it gives the site owners more control over who benefits from a link on their site. On several occasions I’ve had designs stolen and I’ve reluctantly posted links to the perpetrators knowing that the link would give them a PR boost. Now site owners have the ability to link to whoever they want without giving that site a PR boost.

On the surface this seems like a good idea. However I wonder if people will go overboard. Not wanting to give away their precious PR, many site owners may mistakenly start applying this attribute to all their links. I say mistakenly because outgoing links are also beneficial to your own PR in a roundabout way. Alternatively some people may still link normally to high PR sites but try to minimise PR leaching by applying this attribute to low PR sites. I’m sure some clever SEO’s are already thinking of ways to use this attribute to maximise a sites PR.

The other concern is that people will start selectively using this attribute depending on their feelings for a site. Rather than all links being created equal, some will be more important than others. You could probably forgive web developers for using this attribute when linking to Microsoft but how would you feel if the next time somebody linked to your blog they used this attribute because they didn’t like something you said in recent post? I could see things getting messy fast and this anti spam method could have far wider implications.

Posted at January 21, 2005 12:28 AM


JD said on January 21, 2005 3:13 AM

Agreed. I am surprised that everyone is finding more abuses about ‘nofollow’ than it’s advantage. And let’s be honest to ourselves, ‘nofollow’ isn’t going to stop ANY SPAM just like email filters didn’t stop spam. Why don’t we think about solution to fight automated comment spam rather than taking shortcuts.

P.S.: I also think that Google introduced it because they are already incapable of handling blogging and links it generates. My thoughts on this are here.

Michael Heilemann said on January 21, 2005 6:55 AM

I agree, it’s a very dangerous road they’re moving down. I see uses for the property, but overall I think calling it a ‘spam prevention filter’ is something of an overstatement. It’s more like a ‘protection scheme for pagerank’.

Here’s my spin.