Having read this entry, I decided I should put this up for those who might want help in doing the same.
Here is how.
1. Click on the Settings link (upper right corner of page, next to Users link)
2. Click on Discussion link at top of page
3. Scroll down to Comment Blacklist box, paste the IPs in it. You could also type in words (words in its content, name, URL, e-mail, or IP. It will match inside words, so “press” will match “WordPress”.) you find offensive too
4. Don’t forget to hit button on the page.
Let us all do away with trolls
To add the image to your side bar:
1. Click on Design link on the settings page.
2. Click on the Widgets link.
3. Add text from the list of available widgets.
4. Then click on the edit link provided in the text widget that is added to your sidebar
5. Copy paste the following to
<span><img src=”http://mirrorcracked.files.wordpress.com/2008/10/trolls.jpg” align=”center”><br/></span>
6. Click on the save changes button.