A Martian packet is an IP packet seen on the public Internet that contains a source or destination address that is reserved for special use by the Internet Assigned Numbers Authority (IANA) as defined in RFC 1812, Appendix B Glossary (Martian Address Filtering). On the public Internet, such a packet either has a spoofed source address, and it cannot actually originate as claimed, or the packet cannot be delivered.[1] The requirement to filter these packets (i.e. not forward them) is found in RFC 1812, Section 5.3.7 (Martian Address Filtering).
Martian packets commonly arise from IP address spoofing in denial-of-service attacks,[2] but can also arise from network equipment malfunction or misconfiguration of a host.[1]
In Linux terminology, a Martian packet is an IP packet received by the kernel on a specific interface, while routing tables indicate that the source IP is expected on another interface.[3][4]
The name is derived from packet from Mars, meaning that packet seems to be not of this Earth.[5]