We have an FTPS (FTP over TLS) server setup. I am seeing consistent hacker attempts to log in and access the server. I fear that if one of our partners attempts to use regular FTP (without encrypting username/passwords), they will compromise their credentials to our FTP server even though they will be denied access. Although I know SFTP is the most secure route, some of our trading partners don't support SFTP.
What are some best practices to block all of this hacker traffic to our FTPS server?
Should we go the route of "allowable" IPs and only allow traffic from our trading partners Clients' IP?
Would love to hear other's thoughts on this.