The name Martian is given to the hypothetical native inhabitants of the planet Mars.
There have been many fictional depictions of Martians in the past, including the famous invaders from H. G. Wells' novel The War of the Worlds, and also many people who have believed in the existence of real Martians. At this point in time it is generally accepted that Mars has no macroscopic native life, and even the presence of bacteria-scale life is speculative at best.
In a computer network, packets with source addresses not routable by some computer on a network segment are referred to as martians or "packets from Mars", on the grounds that they are of no evident "terrestrial" (i.e. normal) source. Martian packets can arise from network equipment malfunction, misconfiguration of a host, or simple coexistence of two logical networks on a single physical layer. For instance, if the IP networks 192.168.34.0/24 and 10.2.3.0/24 network operate on the same Ethernet segment, packets from 10.2.3.4 are Martians to the computer at 192.168.34.9, and vice versa.
The Martians were a group of physicists and mathematicians who emigrated from Hungary to the United States in the early half of the 20th century. They included Leo Szilard, Paul Erdos, Eugene Wigner and Edward Teller. They received the name from John von Neumann who half-jokingly suggested that Hungary was a front for aliens from Mars.