As the name suggests, the NULL scan sets all the header fields to zero (null). These kinds of packets are not authentic, and some of the targets do not know how to handle this packet. These targets could be your windows machine, and when you scan them using NULL packets, they produce undependable results.XMAS ScanXMAS scan has the same nature as the NULL scan, as both of these are hard to detect. The implementation of the TCP stack will prevent windows from responding to the Xmas scans. The XMAS scans are used to operate the FIN, URG, and PSH flag present in the TCP header.