(第1空)Network security is the protection of the underlying networking infrastructure from ( )access, misuse, or theft, It involves creating a secure infrastructure for devices, users and applications to work in a ( ) manner. Network security combines multiple layers of defenses at the edge and in the network. Each network security layer implements ( ) and controls. Authorized users gain access to network resources. A ( ) is a network security device that monitors incoming and outgoing network traffic  and decides whether to allow or block specific traffic based on a defined set of security rules. A virtual ( ) network encrypts the connection from an endpoint to a network, often over the internet. Typically a remote-access VPN uses IPsec or Secure Sockets Layer to authenticate the communication between device and network.