How do I deal with Spam comments on my WordPress blog?

On WordPress.com, they automatically filter spam comments using a
plugin called Akismet.  Sometimes spam comments aren’t marked as such.
Mark them as spam to help Akismet block comments from that bot.

On a self-hosted WordPress blog (WordPress.org), you need a
WordPress.com API key to activate the Akismet plugin, which comes with
WordPress.  To get the API key, register with WordPress.com.  Once
you’ve registered, sign in and go to http://www.wordpress.com/profile to see your profile.  Your API key will be at the bottom of this page.

If Akismet isn’t working for you, other spam-fighting plugins include Bad Behavior (
http://www.bad-behavior.ioerror.us/ ) and Spam Karma ( http://unknowngenius.com/blog/wordpress/spam-karma/).

Finally,
you can use WordPress to filter comments that include specific words,
marking them for moderation or as spam.  Under Options > Discussion,
you can type these specific words in the Comment Moderation box to mark
the comments for your moderation.  To automatically mark these comments
as spam, enter the words in the Comment Blacklist box instead.  (You
can retrieve "false positives," or comments that do not actually spam,
from the Akismet Spam submenu under the  Comments menu.)

And yes, I get X-rated spam comments on my blog every day.
For a while, I received more than fifty spam comments a day.  Akismet
caught nearly all of them.  The few that it didn’t catch were often
flagged for moderation automatically.

Good luck.  You can’t stop the spam comments from coming in,
but you can make sure that the spammers attacking your site don’t get what they want!