Ah, comment spam. Originally, comment spam was pretty darn effective.
Google and other search engines ranked how many sites linked to another site to decide how valuable that site is. Spammers took advantage of the open nature of blog commenting to comment on blog posts including a link to their spamvertised site and the link was counted the same as if the blog owner linked to it as far as the “weight” and importance it was given. Automate that puppy and suddenly, your site seems really popular.
Google caught on, and introduced the “nofollow” tag to attempt to stop the rampant spamming, and blog software developers quickly introduced this tag into links that were put in comments automatically in the hopes that if you took away the purpose behind the comment spamming, they would all just go away and find something new to do. Yahoo and Bing soon followed and, theoretically, the introduction and mass adoption of the “nofollow” attribute should have given folks no reason to comment spam.
So, why do it now when the spamvertised links don’t even get indexed?
The fact remained that spammers really couldn’t have cared less if the link was going to count for anything, eventually. They got the link in front of eyeballs, and so the effort (which had already been automated) is still worth while even after the SEO juice got yanked.
What Hosts Do
On this, the low cost hosting companies are not terribly effective from a server perspective.
While spam filtering at the gate can get about half to three quarters of the garbage trying to get through, with spam comments effectiveness comes up against your desire to pay a small amount for a lot of web site and the fact that in order to filter out spammers hosts have to filter every, single, solitary request to the web server and run it against hundreds to thousands of signatures each and every time.
As you can imagine, that takes an enormous amount of resource power, so hosts may make an attempt to balance effective filtering with the limitations of needing the server to run fast. Unfortunately, doing it that way, lots can still get through and that puts the onus on you.
What You Can Do
Moderate all of your comments. If you have to approve every, single comment, you are going to be guaranteed that no spam comments make it to your blog. While spam comments are annoying, they also make your blog look unprofessional. You don’t want to leave them there.
Utilize spam fighting plugins – all the top blogging software have them, and many of the services and software give you pages on recommended tools, and others have added to the body of information on this:
In short, a quick search for combating comment spam yoursoftware will likely turn up multiple tools, tricks, and plugins that will help you deal with the amount of spam on your blog.