An attacker engages in IP-based techniques for the purpose of
						fingerprinting operating systems on the network. By interrogating a
						particular IP stack implementation with IP segments that deviate from the
						ordinary or expected rules of RFC 791, an attacker can construct a
						fingerprint of unique behaviors for the target operating system. When this
						set of behaviors is analyzed against a database of known fingerprints, an
						attacker can make reliable inferences about the operating system type and
						version.