Using Active FTP Clients Through an OpenBSD 3.0 Firewall
Before we go into detail about how to configure OpenBSD 3.0, let's briefly review how the FTP protocol works (and doesn't work). FTP is a very venerable protocol that was definately not designed with security in mind. While it was being developed, the concept of a firewall didn't even exist. Since then, improvements have been made to the FTP protocol to make it easier to secure. Unfortunately, client software packages (at least on the Windows platform) have been slow to adapt to these changes, forcing firewall administrators to develop some sort of workaround.
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