This is actually a pre-defined response I send to customers that have a Joomla site that got hacked. Hopefully this info can help everyone keep their Joomla sites secure and up-to-date.
If you are not sure if a Joomla extension is an old version or not, login to your Joomla Admin Area and go to EXTENSIONS > INSTALL > COMPONENTS. There you will see the current versions of the extensions installed. You can ignore the extensions that have the author “Joomla! Project”. Do a search in Google for the extension name and add the words “Joomla extension” to the search term. I try to find the extensions on the Joomla extension site at http://extensions.joomla.org. There you will find the newest version listed for each extension. All old extensions installed to your site need to be removed or patched. Using old versions leaves your site open to hackers and abuse. I cannot stress how important it is to keep Joomla (and all third party extensions) up-to-date. 95% of the Joomla sites I see that get hacked are due to them using old 3rd party extensions.