These pages contain useful information on how to ensure your FTP server remains secure. For more detailed information on what each option of the security settings, please see FTP.
There are quite a number of things that can be done to enhance the security of your FTP server. First, you can prevent potentially dangerous file types such as 'exe', 'pif', 'scr', 'com' and 'bat' from being allowed onto the server. A very important security improvement is to limit access to your important users by restricting the IPs in which access is allowed. If you intend to keep the FTP server private, you could also change the listening ports to non-standard values, effectively hiding your FTP server. In particular, Remote Administration should be set to a non-standard port to help protect your system from users trying to gain access by guessing your password. Finally, making good use of the built in security features such as Anti-Hammering, SSL and the others will help ensure your files are secured.
Ability FTP Server contains many advanced features which are intended to make the software flexible. However, in a lot of cases, some are not required. We recommend that to ensure security is at its best, you disable services which are not used (e.g. if you don't use File Execution or Site to Site transfers then disable them). With fewer services running, there are fewer portals for hackers to attempt a break in. This does not only apply to our FTP server; other services such as web servers, mail servers, windows file sharing and others can also be streamlined.
As well as limiting the services that you run on your server, it is also a good idea to use a firewall to restrict access to only the ports needed. This way you can be sure that there are no ports accessible through flaws in Windows or other software. You should always build your security by starting with a 'brick wall' (firewall) around your server then letting through just the bits you want as and when they are needed.
See Also: FTP.