Bogon filtering

What is Bogon Filtering?
Bogon filtering is the release of fake IP address components. A bogon is a type of URL reference that has been found typical of certain types of Denial of Service attacks and atypical in legitimate network traffic.

Bogons are often viewed as illegitimate on the Internet with address prefixes or components. For this purpose, Bogon filtering is a way of filtering out data traffic that can be illegitimate or even dangerous.
Various firewalls and other tools use bogon filtering to eliminate these often malicious addresses and ISPs can provide this type of service to users. The name bogon has its roots in the words 'bogus' and 'bogosity' and is a generally accepted part of IT slang.