The internal factors that can aid an attacks are your employee, former employee, business associate or third party contractor.
You can never be over secured because vulnerability are being discovered on daily basis will will make the new software that you just installed to start asking for updates or security patches.
In this 21 century, someare thinking that there is no need for cyber security expert in there firm because there has not been any attack for more than 20 years.
The employee that you denied access to his physicsl/medical need will leverage your company trade secret in exchange for extra cash .
Hakuna Matata ... Derek