Apply the security after the split. I don't secure the BE but make it a hidden file on the server and select the option to hide the DB window on open. If anyone ever messes with it I will place an On Open form requiring a password (been posted here before how to do this) but I wouldn't use Access security on the BE.
Now, here's how I handle distribution. I create a batch file that copies the FE to everyone's machine. I locate the .mdw file on the server. The batch file opens Access, loads the db and joins the appropriate workgroup.
I've posted detailed instructions on this recently so search for user "Autoeng" and keyword "security" or post back with any problems you may have. To find the BE security I was talking about search for keyword "backend security".