Here i am with a new working hack to scan and exploit a Joomla blog. Things you needed are following :--->
Here are following steps, please follow all the steps according to this post:
1. Click on Applications/Backtrack/Vulnerability assesment/Web Vulnerability assessment/CMS Vulnerability Identification/joomscan.
2.Now Joomla scanner console will open like in image.
4.Now type ./joomscan.pl -u www.YourJoomlasite.com in this in place of YourJoomalasite.com type your desired joomala site and hit enter it will start scanning it .
This article is written by Aditya Joshi, He blogs at http://adityahackingarticles.blogspot.in . If you are intrested in writing article too then email me your article at firstname.lastname@example.org