Once the network perimeter has been secured, organizations can still not be sure that the network is secured. This is because the endpoints themselves are a potential source of attack. The endpoints have USB ports, which can be used by an employee to transfer a malicious file unknowingly, or the system might be running an older operating system version, which might be susceptible to security attacks.
We have covered NAC briefly under the section on network access earlier in the chapter. In addition, having strong organizational security policies for operating systems and other endpoint protection systems go a long way in securing the overall enterprise.