I found another thing that will help with this: locking the flash files to your domain.
If you secure them in the DNN secure folders, they can only be downloaded by users with the appropriate permissions. However, those users can then distribute the flash files.... So, if you put the following actionscript on the first frame of the flash file, it will lock it to your domain (note that you need to replace the generic domain with your domain name into the action script before you publish it)
//Check to see that it is playing from MyDomain.com domain
//Note that there are local folders listed as acceptable domains.
//If you don't have these in the script, then you won't be able to
//preview the flash file locally before you upload it to your domain.
okToPlay = false;
siteURL = "http://www.MyDomain.com";
siteURL2 = "https://www.MyDomain.com";
localURL1 = "C:\\Your Flash Preview Folder\\Published";
localURL2 = "file:///C:/Your Flash Preview Folder/Published";
localURL3 = file:///C:/Your%20Flash%20Preview%20Folder/Published;
if ((_root._url.substr(0,siteURL.length) == siteURL) || (_root._url.substr(0,siteURL2.length) == siteURL2) || (_root._url.substr(0,localURL1.length) == localURL1) || (_root._url.substr(0,localURL2.length) == localURL2) || (_root._url.substr(0,localURL3.length) == localURL3))
{
okToPlay = true;
}
if (okToPlay == false)
{
_root.unloadMovie();
}