Information Security Concepts and Secure Design Principles

Threat modelling is the structured practice of asking what could go wrong with a system, who would make it go wrong and how, while the design can still be changed cheaply.

Phishing is an attack that deceives a person into revealing credentials, approving a payment or running malicious content, usually through a message that impersonates someone they trust.

Ransomware is an attack in which criminals gain access to an organisation's systems, encrypt or steal its data, and demand payment to restore access or withhold publication.

Switching is the forwarding of frames within a single network segment by a device that learns which hardware address sits on which port and sends each frame only where it needs to go.

A VLAN divides one physical switched network into several logical segments, each with its own broadcast domain, by tagging frames with a VLAN identifier so that ports and devices in different VLANs cannot reach each other without a router.

Network address translation rewrites the addresses and ports in packets as they cross a network boundary, most commonly so that many devices with private addresses can share one public address to reach the internet.

Load balancing is the practice of putting one entry point in front of several interchangeable servers and distributing incoming requests among them by a chosen policy, so that no single machine carries the traffic and no single machine's failure takes the service down.

A CDN is a worldwide network of servers that answers requests for your site from a location near the person asking, instead of sending every request back to the single machine your site runs on.

DNS is the distributed lookup system that turns a hostname such as getting-digital.net into the IP address a browser can connect to, by walking a chain of nameservers whose answers are then cached for a lifetime the domain's owner publishes.