When I open a "URLLink.acsm" file, from the <src> or from <thumbnailURL> i can get the actual source file name ie: packed eg: <src>http://mydomain.com:8080/bookstore/5e9742de-6513-4a5c-8dd2-bcffee59d912.epub</src>. Using this link directely i can download the original file packed. Can it blocked ? Is there any security property in ACS 4.1 by which i can block the direct download of files. Is these packed files are in enrypted format, so that if any one download, he can't able to view that ?
Those files are encrypted files that you already packaged. You can only open those files with a valid liscence from the content server.