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Security measure 1:
Every directory should contain an index file by renaming the default page you wish to be shown to index. Ensure that all the internal links are updated to that page also.

Security measure 2:
Create an empty index file. When arriving at the directory, a blank page will be displayed, but you will no longer be showing a directory listing. Provide a message and a click-able link here to draw your visitors to the correct page.

Security measure 3:
Create an index file containing a redirection to the page you wish to be shown. There are many easily implemented and free code snippets at your disposal allowing you to do this and your viewers will probably not even notice there is a redirection taking place.

Security measure 4:
Do not keep any of your download-able content which people pay for in the same directory as the sales page. Keep it in a secure directory separately and set up your payment processor to that particular directory. This ensures that only people who have subscribed for the content can gain access to it. You are more likely have people trying to get a hold of your restricted content without having to pay for it when you are selling products on line as an Internet Marketer but adhering to these 4 basic measures of security will assist you to dramatically lower the risk of unlawful access to your website and make life much less of a worry in the long run.