Nat
Network address translation (nat) is an approach that is used to remap an IP address space into another by modifying network address information in ip datagram packet headers while they are in transit. This technique was originally used for rerouting traffic in ip networks without renumbering every host. Typically home or small business networks use nat to share a single dsl or cable modem ip address. However, in some cases nat is used for servers as an additional layer of protection.
National institute of standards and technology nist
The national institute of standards and technology (nist) is a non-regulatory federal agency within the U.S. department of commerce. NIST’s mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.
Natural disaster
Natural disasters are any act of god or natural event caused by environmental factors. Some examples of these disasters include fire, flood, earthquake, lightning, or wind and disables the system, part of it, or a network of systems.
Netmask
A netmask is a string of 0’s and 1’s that screens out the network part of an ip address so that only the host computer part of the address remains. The binary 1’s at the beginning of the mask turn the network id part of the ip address into 0’s. The binary 0’s that follow allow the host id to remain. In a netmask, two bits are always automatically assigned. For example, in 255.255.225.0, “0” is the assigned network address, and in 255.255.255.255, “255” is the assigned broadcast address. The 0 and 255 are always assigned and cannot be used.
Network based ids
Network-based intrusion detection systems (nids) are placed at a strategic point (or points) to monitor the traffic on the network. It analyzes the passing traffic on the entire subnet, and matches the traffic that is passed on the subnets to the library of known attacks. When an attack is identified, or abnormal behavior is detected, an alert is sent to the administrator. Opnet and Netsim are commonly used tools for simulation network intrusion detection systems.
Network mapping
Network mapping is the study of physical connectivity of networks. It is used to compile an electronic inventory of the systems and the services on any network. With the increase in complexities of networks, automated network mapping has become more popular.
Network taps
Network taps are hardware devices that help in accessing the data flow across a computer network. It is also desirable for a third party to monitor the traffic between two points in the network. The network tap has (at least) three ports, an a port, a b port, and a monitor port. Network taps are generally used for network intrusion detection systems, voip recording, network probes, rmon probes, packet sniffers, and other monitoring and collection devices and software that require access to a network segment.
Non printable character
A non-printable character is a character that doesn’t have a corresponding character letter to its corresponding ascii code. Examples would be the linefeed, which is ascii character code 10 decimal, the carriage return, which is 13 decimal, or the bell sound, which is decimal 7. On a pc, you can often add non-printable characters by holding down the alt key, and typing in the decimal value (i.e., alt-007 gets you a bell). There are other character encoding schemes, but ascii is the most prevalent.
Non repudiation
Non-repudiation refers to the ability of a system to prove that a specific user and only that specific user sent a message and that it hasn’t been modified. On the internet, a digital signature is used not only to ensure that a message or document has been electronically signed by the person, but also, since a digital signature can only be created by one person, to ensure that a person cannot later deny that they furnished the signature.
Null session
A null session is also known as anonymous logon. It is a method that allows an anonymous user to retrieve information such as user names and share this over the network, or connect without authentication. Null sessions are one of the most commonly used methods for network exploration employed by “hackers.” A null session connection allows you to connect to a remote machine without using a username or password. Instead, you are given anonymous or guest access.