Networking Fundamentals Every Security Professional Needs

You cannot secure what you don't understand at the packet level. This lesson covers the parts of networking that matter operationally: the TCP three-way handshake and why SYN floods exploit it, the OSI/TCP-IP model as a mental map for where controls actually sit (a WAF operates differently than a network firewall because they sit at different layers), DNS resolution and why DNS is such a common exfiltration and C2 channel, and how NAT and routing affect what an attacker can reach from a given foothold.

Practically: when you read a pcap or a firewall log, you should be able to reconstruct the conversation — who initiated it, what protocol, and whether the pattern is normal for that host. That skill underlies almost everything else in this course.