I would recommend that you find some way to protect your admin directory so random people don't clear your cache and reload the WURFL file .htaccess is one way to do it, yes; however, I'm assuming you are using a control panel for your hosting provider like Plesk or Cpanel. There should be an easy-to-use method of password-protecting directories within the control panel. I just did this for a client using Cpanel the other day and it was very easy.
These links might be helpful to you:
http://www.siteground.com/tutorials/cpa ... tories.htm
http://download1.sw-soft.com/Plesk/Ples ... 03s68.html