Network Security is the practice of adopting and enforcing policies and controls that allow you to monitor and prevent unauthorised access, misuse, modification or denial of network accessible applications and resources. Network security involves the authorisation of access to resources on the network and this control is managed by a network administrator. Access by the user is typically allowed by means of a username and password. Stronger authentication mechanisms (such as two-factor authentication) are often put in place to increase the secure accessibility to the network. Once authenticated, Firewalls then typically act as the next line of defence enforcing access policies specific to the users credentials. Whilst firewalls enforce policies, they typically cannot detect harmful payloads (such as Trojans) within that access, so organisations will then rely on Anti-Virus Software and Intrusion Detection/Prevention products to detect and inhibit the proliferation of such Malware. Communications are often encrypted between the user and the network.