Core FTP

I've been using FileZilla FTP Server for awhile, and in needed for SFTP. Installed Core-FTP server for testing, and in 2nd day I'm getting several login attempts from various IP addresses with random user names. Has anyone encountered this issue? Is there a security issue with Core-FTP?

Unless you are filtering out all addresses except customer IPs, then anyone will be able to attempt a connection to your server.

If not using access rules, simply switching to a non-standard port will eliminate most of the connection attempts (mostly by bots, hackers, etc)