Mikrotik Port Service FTP 21 - MikroTik Script RouterOS
Mikrotik provides a standard FTP service that uses ports 20 and 21. FTP is usually used to upload or download router data, such as backup files. FTP authorization using router account user & password. This FTP port is often attacked using BRUTE FORCE, you can change the port or disable it when not in use.
# FTP Port Enable
/ip service set ftp port=21 address=0.0.0.0/0 disabled=no
# FTP Port Disable
/ip service set ftp port=21 address=0.0.0.0/0 disabled=yes
Credit: mikrotik.co.id