You can disable Anonymous Ftp through WHM in Cpanel Server.

Login to WHM as root, In Service Configuration menu, click on FTP Configuration

You will see a button to disable Anonymous Ftp

Main >> Service Configuration >> FTP Configuration
Disabling Anonymous Ftp
Complete!! Ftp Password Files synced Vhost Passwords synced
Attempting to restart ftpserver
Waiting for ftpserver to restart…. . . . . . . . . . . finished.

ftpserver status

root 21467 0.0 0.2 2752 1848 ?? Ss 6:51PM 0:00.03 pure-ftpd (SERVER) (pure-ftpd)

ftpserver started ok