Setalah tahu gimana cara attack dengan metode brute force, sekarang cara penangkalnya pada mikrotik. Cukup buat 3 buah rule di firewall sbb:

/ ip firewall filter
add chain=input in-interface=ether1 protocol=tcp dst-port=21 src-address-list=ftp_blacklist action=drop

# accept 10 incorrect logins per minute
/ ip firewall filter
add chain=output action=accept protocol=tcp content=530 Login incorrect dst-limit=1/1m,9,dst-address/1m

#add to blacklist

/ ip firewall filter
add chain=output action=add-dst-to-address-list protocol=tcp content=530 Login incorrect address-list=ftp_blacklist address-list-timeout=3h

Rule diatas akan mebatasi failure login sampe 9 kali.