Detecting IP Address Filters

Until recently IP network operators were encouraged to set up so-called “bogon address filters” at the edge of their networks. These filters were intended to discard all incoming traffic where the source address in the IP header was from a block of addresses that was known to be unallocated. The…

Curious Case of the Crooked TCP Handshake

In this article we will be delving into the behaviour of the Linux implementation of TCP, and looking at the way in which TCP establishes a connection. There are socket options in Linux that cause the TCP handshake to behave in a rather curious way.