In the past few days on this website I found a significant increase in spam in the comments. Fortunately comment did not show up physically on my articles, only those awaiting publication. Because my website is not extremely popular, I can just manually verify approve all comments.
However, if the spam started to come in hundreds a day, it started to become annoying.
First of all, I began to suspect captcha. I changed my plugin to another captcha plugin, with much more difficult to read images. After changing captcha just in next few seconds I got another spam comment. I decided switch comments off until resolving the problem. To do this in settings I allowed to post comments only for people, who have an account on my website. Because users are unable to register on my blog (this option has been disabled), it should automatically disable spamming.
I was really surprised when after next few seconds I got spam in comments again.
A brief search on the internet found that probably the problem was caused by pingback and trackback.
As I do not use this system, I decided to turn it off: “Allow link notifications from other blogs (pingbacks and trackbacks).”
And again, after disabling pingbacks, after just a few seconds, I got a new spam in my WordPress.
So far the good solution is to change file wp-trackback.php to another different name.
As far as I know it works!
Screw you spammers!!!
Edit:
Another option to kill the spam has been described here.