Description
By default WordPress creates an administrator user account named admin. Using the default Admin WordPress Account, hackers can easily launch a brute force attack against it. In order to help deter this type of attack, you should change your default WordPress administrator username to something more difficult to guess.
Remediation
Change the default WordPress administrator username to something more difficult to guess. Consult web references for more information.
References
OWASP Wordpress Security Implementation Guideline
Your WordPress Installation Is Using the Default Admin Account