The built-in administrator account must be disabled.

The built-in administrator account is a well-known account subject to attack. It also provides no accountability to individual administrators on a system. It must be disabled to prevent its use.

Verify the effective setting in Local Group Policy Editor. Run "gpedit.msc". Navigate to Local Computer Policy >> Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options. If the value for "Accounts: Administrator account status" is not set to "Disabled", this is a finding.

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Accounts: Administrator account status" to "Disabled".