Over the last 30 - 60 days we have started to see an alarming increase in exploits targeting Joomla and WordPress php scripts.
Joomla version 1.x is in no longer maintained by Joomla, and now has several known exploits that have been automated, WordPress has similar problems.
We urge you to upgrade any Joomla / WordPress installations you may have on your hosting account as soon as possible. If you have installed a Joomla / WordPress and are not using it, we would recommend removing the installation.
Upgrading Joomla version 1.x to 2.x is not 'straight forward' Joomla have created a guide on how to do this here: http://docs.joomla.org/J2.5:
If you are using an old version of WordPress or Joomla and do not upgrade them, then your websites are at risk.
If you do not have Joomla or WordPress in use on your web hosting you can safety ignore this message.