N

NAK

Negative acknowledgment. A response sent from a receiving device indicating that errors were contained in the information received.

NetBIOS

Network Basic Input/Output System. A transport protocol connecting network hardware with the network operating system.

network sniffer

A tool for monitoring and recording network traffic.

Network Basic Input/Output System

See NetBIOS.

Null scan

A packet sent to a TCP port with no Layer 4 TCP flags set.