Reverse Proxying of FTP?

[Firewalls <Firewalls () exchange ware net>]

Hi folks,

We are looking for a simple solution to allow internet users to access
an FTP server on one of our
customers' internal networks. For obvious reasons they would prefer not
to allow direct access to
their FTP server. 

I'm looking for a moderately simple, and sercure mechanism such that
their FTP server would only
have to talk to one IP address (that of our FTP proxy).

Any suggestions?


TIA,
Lance