Sometimes you don't have the time to invest on your blog and you keep days or weeks without posting or even moderating comments.

For that reason, one of the thing you may want to do if you receive lots of spam comments is to temporarily close the comments for all posts.

Akismet is a good plugin and blocks lot of spammy comments but sometimes it lets some spam pass and if you don't have much time to moderate comments this is the less effort solution.

And then, when you have the time again to dedicate to your blog you will want to open the comments again.

Here's a tip of how you can do it.

Go to your mysql command line or your phpmyadmin and execute the following command:

UPDATE wp_posts SET comment_status = ‘open' WHERE comment_status = ‘closed';

The same way, if you want to just close all your comments, you can use:

UPDATE wp_posts SET comment_status = ‘closed' WHERE comment_status = ‘open';

Note that this command will apply to all of your existent posts. They will all have the comments on/off depending on the command. To affect the future posts, you need to go to your WP Admin console under Options>Discussion and check/uncheck the "Allow People to Post comments on the Article".