Explicit is less secure because after the initial handshake skips encryption during data transfers, while the Implicit keeps the encryption of the data after handshake too.

Please note that SFTP is completely different from FTPS.

I know this is an extremely old thread, however. With these answers, you can start configuring your firewall. Have they locked down the DATA channel to a single inbound port? Have they locked down the DATA channel to a small range or ports? Assuming the server only works in PASV (passive) mode, you need to figure out how the server is configured to allocated DATA ports. You need to find out which port is the Control Connection. To know exactly what ports you will need to open, you will need to either:Ī) talk to the vendor to get specifics about how their system has been configured.ī) Use a protocol analyzer, such as tcpdump or wireshark, to look at the traffic, both from outside your firewall and inside your firewall If your client machine has a static address or is being statically NATed, you may not need to make any firewall changes, assuming you allow all outbound traffic and the server operates only in Passive mode (PASV). One thing not mentioned is whether or not your firewall is performing NAT and whether or not it is static NAT or dynamic NAT. Using SFTP, or scp, makes the network administrator's job a lot easier - everything happens on the server's port 22, and the transaction follows the normal client/server model. If that information is secured by SSL, the firewall can't read it or change it.

In an ordinary FTP session, the information about data connections is read, and for NAT modified, by the firewall in order for the firewall to dynamically open the needed ports. My understanding of FTP over SSL (ftps) is that it doesn't work well with firewalls and NAT.

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