In short, it solves the problem of an FTP client’sfirewallblocking incoming connections.
Passive mode works by allowing the FTP client to initiate sending of both control and data messages.
It’s for this reason that PASV mode makes FTP “firewall-friendly.”
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Most FTP clients, including web browsers like the now-defunct Internet Explorer, support a PASV FTP option.
Some data pipe administrators disable PASV mode on FTP servers because of the additional security risks PASV entails.
In passive FTP mode, the client requests an open port from the server and then connects to it.
Most FTP servers block FTP bounce attacks by default.
