4.1Network and Database Fundamentals

SG is not a technical-depth qualification, but understanding controls against unauthorized access and information leakage correctly requires a foundation in networking and data basics. Here we avoid going too deep and focus only on the TCP/IP, DNS, and database points directly relevant to security decisions.

4.1.1TCP/IP and IP addresses

• TCP/IP is the standard protocol suite used on the internet and in-house LANs. It divides roles across four layers—application, transport, internet, and network interface—and each layer faces different threats (eavesdropping, tampering, spoofing) requiring different countermeasures. TCP is connection-oriented, providing reliable communication via a three-way handshake, while UDP is connectionless, faster but without delivery guarantees.
• An IP address identifies a device on a network. Distinguish a global IP address (unique across the internet) from a private IP address (valid only within an organization, not directly reachable from outside). A subnet mask separates the network and host portions, and segmenting a network by department or site is a basic control that limits the blast radius when a device is compromised.