The engineer should close any unnecessary ports, such as port 25 (SMTP) and port 110 (POP3), which are not used by the SFTP server. The SFTP server uses port 22 for secure file transfers, so this port should be left open. The engineer should also bind port 22 to only the internal interface, so that it is not accessible from the public internet. The engineer should also bind ports 137, 138, 139, and 445 to only the internal interface. These ports are used for various networking protocols, such as NetBIOS and SMB, and are not needed for the SFTP server. By binding these ports to only the internal interface, the engineer can further harden the system and prevent external access to these services.