Change default FTP port for greater security for the server and to its contents, if the server is a shared one. Not only because the default port gives you a connection automatically and if they could guess the password, your content is in risk. So, I would suggesto to change the FTP port to a non standard one.

To Change default FTP port to which the FTP service listens to, we need SSH access.

PureFTP#

Login to the server as root, and navigate to /etc

cd /etc
pico pure-ftpd.conf

Search for this line

# IP address/port to listen to (default=all IP and port 21).
# Bind 127.0.0.1,21

and change to the desired value , here, I am going to change it to 21001

# IP address/port to listen to (default=all IP and port 21).
Bind 0.0.0.0,21001

If you want to allow specific IPs, you can enter them in line.

Bind 192.168.1.2,21001
Bind 192.168.1.3,21001

Now restart ftp server

/scripts/restartsrv_ftpserver

You should make sure that traffic through the new port is allowed in firewall to get this operational.

ProFTP#

If you are using proftpd then follow the steps below to Change default FTP port:

Login to ssh via root

Edit /etc/proftpd.conf and change:

Port 21

to

Port 21001

Now restart ftp server

/scripts/restartsrv_ftpserver