Step -1: Go to IIS Manager.
Step -2: At the server level, select the FTP Logon Attempt Restrictions feature.
Step -3: Check Enable FTP Logon Attempt Restrictions option.
Step -4: Enter the maximum number of failed attempts and the time period.
Step -6: Enable Deny IP addresses based on the number of failed login attempts.
Step -7: Click Apply in the Action pane.