I have my WordPress blog at https://diary.vishalon.net. Every day I am getting hundreds of comment spam. I had installed comment spam fight plugin and it seems like worked for few days but again I was getting spam comments. I changed the settings of blog so that only logged in user can put a comment. I even disabled comments completely but all efforts were in vein. I tried to find some information on google but couldn’t get it So I thought let me debug the application and check it out why I am getting hundreds of comments everyday. For this, in wp-comments-post.php file I wrote a code to write all parameters in a text file so I can check out what’s wrong with application. I can post my comment and see the log file but for spam, there was no log trail. It seemed to me that comments are coming from other files. so I moved that code into config file and I found that those comments are actually trackbacks. If you want to check if the comment is trackback or not, check the Email value of comment. If you see it empty, it means it is a trackback. I disabled trackback by login in site > Options > Discussion and disabling trackback and pingback.
Now I am relieved of spam comments(actually trackbacks).