[otrs] Using LDAP authentication and encryption of passwords

I want to use the LDAP authentication module ($Self->{'AuthModule'} = 'Kernel::System::Auth::LDAP') so that customers can use their Active Directory username and password to gain access to their customer panel. I can easily ensure that their password and username are encrypted between their computer and our web server by using a secure (https) web server, but is the connection used by the LDAP authentication module between the web server and the Active Directory domain controller encrypted or in the clear? If, as I suspect, it is not encrypted, is there a way to change it so that it is encrypted? Thanks, A. Lewenburg