I have found that I have a similar attack to the one mentioned here
The file keeps getting recreated and I cannot see from where its coming. How can I fix this? Anyone with a similar experience? I am running joomla 1.5.25
How can I trace the script that includes this file? How do I secure the site?
Yikes, that’s not a good situation. I’ve seen it happen a few times and more often than not the solution was to recreate the website from a clean Joomla install, copy over the data and reinstall components.
However first check that the permissions are ok (no 666, 777, etc) and definitely check the VEL to see if any of your extensions have know vulnerabilities http://docs.joomla.org/Vulnerable_Extensions_List
You could also check on the Inj3ctor database http://www.1337day.com/ .
Most hacks like these happen via out of date extensions, open permissions, or as linuxeasy mentioned a poorly configured host.
Would highly recommend installing jhackguard or eyesite on the website. Eyesite will monitor your files and notify you when changes occur -http://extensions.lesarbresdesign.info/extensions/eyesite