FTP FTP fingerprinting is common among normal users and hackers alike. Most FTP clients contain a few fingerprinting techniques to figure out the server version in order to compensate for some well known bugs.
Hackers use the technique in order to figure out what version the server is running.
There are zillions of exploits for FTP servers, so figuring out the exact version helps the hacker narrow down what they have to do in order to compromise the system. The first way to fingerprint an FTP server is to send the SYST command. In theory, this command should return the underlying operating system version. Another technique is to view the output of directory listings. The original versions of FTP uses text-mode clients where directory listings where read by human beings.