Handling Spam Comments on Your Blog
Spam comments are automatically filtered by WordPress, but occasionally a spam message will slip through. You can mark a message as spam using the following steps:
From the Dashboard page, click the Comments link on the left.
Click the check box to the left of the spam comment to select it. If there are multiple spam comments, select them all.
Select Mark as Spam from the Bulk Actions pull-down menu.
Click the Apply button.
You can control the filtering of messages by changing the discussion settings for your blog by clicking the Settings link on the left, then selecting Discussion from the left navigation column.