An attacker uses a TCP XMAS scan to determine if ports are closed on the
						target machine. This scan type is accomplished by sending TCP segments with
						the all flags sent in the packet header, generating packets that are illegal
						based on RFC 793. The RFC 793 expected behavior is that any TCP segment with
						an out-of-state Flag sent to an open port is discarded, whereas segments
						with out-of-state flags sent to closed ports should be handled with a RST in
						response. This behavior should allow an attacker to scan for closed ports by
						sending certain types of rule-breaking packets (out of sync or disallowed by
						the TCB) and detect closed ports via RST packets. he major advantage of this
						scan type is its ability to scan through stateless firewall or ACL filters.
						Such filters are configured to block access to ports usually by preventing
						SYN packets, thus stopping any attempt to 'build' a connection. XMAS
						packets, like out-of-state FIN or ACK packets, tend to pass through such
						devices undetected. Many operating systems, however, do not implement RFC
						793 exactly and for this reason FIN scans do not work as expected against
						these devices. Some operating systems, like Microsoft Windows, send a RST
						packet in response to any out-of-sync (or malformed) TCP segments received
						by a listening socket (rather than dropping the packet via RFC 793), thus
						preventing an attacker from distinguishing between open and closed
						ports.1. Speed: TCP XMAS scanning is fast compared to other types of
							scans2. Stealth: TCP XMAS scanning was once stealthy, but is now easily
							detected by IDS/IPS systems3. Open Port: Detects an open port via no response to the
							segment4. Closed Port: Detects that a closed via a RST received in response
							to the FIN5. Filtered Port: Cannot distinguish between a filtered port and an
							open port6. Unfiltered Port: Cannot distinguish between an unfiltered port and
							a non-stateful filtered port