Very secure if you're using a strong hard to guess password.  You can make it even tougher by using cPanel Brute Force Protection or Configserver Firewall to limit the number of failed logins and block/ban as well. 

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Thanks Infopro, I always use 8 character passwords with mixes of all the available characters.  I also have the complete configserver package and like it.  Tough learning curve however.  I'll research the brute force protection you mention. 

You might also want to consider cPanel > Leech Protect along with Password Protect Directories.  Leech Protect works in conjunction with Password Protect Directories (it requires the directory be password protected first), and it can be configured to only allow a set number of logins per 2 hour period.  It can also alert you whenever a user has been redirected to an alternate url (when hitting the 2 hour timelimit).