The default Super Administrator account which is created during the Joomla installation, is called “admin”. You do protect it with a password at the final steps of the installation,
but still leaving the username to this well known default value exposes 50% of the security of the username/password combination.
This is why we advise you to change the name of the default Super Administrator account to something more difficult to guess.
Step 1: Log into your Joomla admin panel.
Step 2: From the menu select User Manager.
Step 3: Select the ‘admin’ user record.
Step 4: Change the value in username. (Good usernames contain both letters and numbers.)
Step 5: Save the changes.