If you use WordPress as your blogging platform and tired of receiving tons of viagra and related SPAM, bot generated comments, make use of the WordPress Comment Blacklist feature. You can find this feature in
Admin CP >> Options >> Discussion.
You can use this feature to stop almost 95% SPAM messages. I’ve been using this option for past couple of months and find it pretty helpful. Just add ‘viagra’ and similar words in the Comment Blacklist box and see the magic!