Many users do something that's unfortunately very common... they forget to update / upgrade their site with the latest software and usually they discover that when their website gets hacked.
Specially with older Joomla versions such as 1.5.x but even now with the latest Joomla version 2.5.x

The good news is that in the latest version Joomla added a very useful feature (similar to WordPress) and when a new update is out you are getting notified about the available updates and you just have to press ....update in order to keep your website safe.

But in some cases this is just not enough!

Here's a really good website that adds some more security checks to your website and gives your even more assurance about your websites health.
We suggest that you make use of this http://sitecheck.sucuri.net and be able to check your website security (use this as one more of the tools you use for your security) .

If you have any kind of questions we are always here to help you!