Port scan detect (PSD) | PSD Mikrotik tutorial 

Port scan detect (PSD) is an option in the Mikrotik firewall that allows you to detect port scan events.
MikroTik can evaluate and block port brute force, which is usually carried out by various port scanners that can be used by attackers.
Basic research into the security of your router and further development of the attack vector usually begins with the attacker launching some kind of port scanner, for example, Nmap, and starting to check open ports on your system. After he checks these ports, he can already begin to develop certain attacks.