In this chapter, you learned that today's open networks introduce a need for network security that previously was less urgent. The network security policy, as defined by RFC 2196, is a core component of an organization's security implementation. The policy supports the organization's primary security objectives, defining who will be allowed access, who will be denied access, and what the policy is aiming to protect. The Cisco Security Wheel is a visual tool to represent how network security technologies support the continuous process of improving and updating a network security policy. Finally, we reviewed types of attacks and commonly used tools and methods , together with a short recommendation on how these kinds of attacks can be prevented.