Glossary For Access Control

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National Electrical Code (NEC) A consensus standard published by the National Fire Protection Association (NFPA); commonly called "code".

Noise : The unwanted and/or unintelligible signals picked up on a cable circuit.

Normally open (NO) : The condition or position of contact prior to initiation or energization, in this case, an open condition.

Normally Closed (NC) : The condition or position of contact prior to initiation or energization, in this case, a closed condition

NAT : Network Address Translation. It is used to share one or a small number of publicly routable IP addresses among a larger number of hosts. The hosts are assigned private IP addresses, which are then "translated" into one of the publicly routed IP addresses. Typically home or small business networks use NAT to share a single DLS or Cable modem IP address. However, in some cases NAT is used for servers as an additional layer of protection.

Network Address Translation : The translation of an Internet Protocol address used within one network to a different IP address known within another network. One network is designated the inside network and the other is the outside.

Network Mapping : To compile an electronic inventory of the systems and the services on your network.

Network Taps : Network taps are hardware devices that hook directly onto the network cable and send a copy of the traffic that passes through it to one or more other networked devices.

Network-Based IDS : A network-based IDS system monitors the traffic on its network segment as a data source. This is generally accomplished by placing the network interface card in promiscuous mode to capture all network traffic that crosses its network segment. Network traffic on other segments, and traffic on other means of communication (like phone lines) can't be monitored. Network-based IDS involves looking at the packets on the network as they pass by some sensor. The sensor can only see the packets that happen to be carried on the network segment it's attached to. Packets are considered to be of interest if they match a signature.Network-based intrusion detection passively monitors network activity for indications of attacks. Network monitoring offers several advantages over traditional host-based intrusion detection systems. Because many intrusions occur over networks at some point, and because networks are increasingly becoming the targets of attack, these techniques are an excellent method of detecting many attacks which may be missed by host-based intrusion detection mechanisms.

Non-Printable Character : 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 is the ability for a system to prove that a specific user and only that specific user sent a message and that it hasn't been modified.

Null Session : Known as Anonymous Logon, it is a way of letting an anonymous user retrieve information such as user names and shares over the network or connect without authentication. It is used by applications such as explorer.exe to enumerate shares on remote servers.

Creating Simplicity out of Complexity