Definition - What does Bogon mean?
A bogon is an bogus IP address from the bogon space, which is a set of IP addresses not yet officially assigned to any entity by the Internet Assigned Number Authority (IANA) or a regional Internet registration institute.
Bogon IP addresses are legitimate addresses. You may see a bogon IP address as a result of a misconfiguration (whether intentional or unintentional) that fools a recipient about a sender's legitimate IP address. Bogon IP addresses are popular in hacking or malicious activities and are used by spammers and those who initiate distributed denial-of-service attacks. As such, many Internet service providers and firewalls block bogons.
A bogon is also known as a bogon space or bogon IP address.
Techopedia explains Bogon
IP addresses are the core component of the entire Internet and intranet infrastructure throughout the world. They provide a means to uniquely identify a website, server or any other connected device or appliance. These addresses are used to perform communication between clients and applications.
IANA allocates unique IP numbers/addresses to every such instance and node residing over this heterogeneous network. The range of IP addresses allocated or registered to any entity are part of the IP address reserved space. On the other hand, any other address that is part of the address space but is not yet registered is from the bogon space. Any address in the bogon space is known as bogon or a bogon IP address.
Bogon space IP addresses are not normally visible over the Internet or on any computer network, but they are still exploited, mostly for illegal or fraudulent activities. Hackers manipulate the source IP address to a bogon IP, giving the receiver the impression that the packet is arriving from a reliable source.