You can increase your security using FTP by creating virtual users. These users can use FTP but they are limited in access to the system as a whole. More here
If you create user accounts on a server, and then allow people to log on to the ftp server under those accounts, there’s a chance that some hacker could find a way out of the chroot jail. That would allow him to access areas of the file system where he has no authorization, and possibly to plant Trojans or other malicious programs.