OpenCyber AcademyLearning outcomes
You will (1) describe the parts of a computer system; (2) explain how services run on hosts; (3) relate hardware and software to security.
1.1 A technologist's view
Tomás Rivera starts the three-year technologist programme at the fictional Greystone Polytechnic, where courses mix theory with hands-on work for real organisations. His work placement partner later in the course is the fictional Ridgeway Secondary School, which has about 1,200 students, 110 staff and one IT technician, Gareth Pryce. His lecturer, Hannah Okafor, begins with computing systems because every network control eventually protects some computer: a laptop, a server, a printer or a switch. Understanding what those computers do makes it easier to see what the network must allow and what it should stop.
1.2 Hardware, firmware and software
A computer system has layers. Hardware includes processors, memory, storage and network interfaces. Firmware is low-level software built into devices that starts them and controls hardware; switches, printers and wireless access points run mostly on firmware. Operating systems manage resources and run applications, which provide the services people use. Each layer can have weaknesses and needs updates. Tomás notes that school printers and projectors run firmware nobody has updated in years, which matters because those devices sit on the same network as student laptops and could be misused if they have known flaws.
1.3 Services and clients
Many systems act as servers, offering services that clients use. The school's file server offers shared folders, the web server hosts the school's site, and the print server accepts print jobs. Each service listens on a network port and waits for requests. Clients, such as student laptops, start connections to those services. Tomás learns to describe each system by the services it offers and the clients it serves, because network rules are written in exactly those terms: which clients may reach which services on which ports, and which may not.
1.4 Why inventory comes first
Tomás cannot protect systems nobody has listed. With Gareth's permission, he begins an inventory of the school's main systems: servers, switches, access points, printers and projectors, with their roles, locations and owners. The CIS Controls put inventory of enterprise assets first because every later safeguard depends on it. Within a day, the inventory reveals a small server in the science department that nobody remembers setting up. Gareth investigates and finds an old data-logging system, still running and still connected to the student network, which goes on the list for review.
Worked example
Tomás's first inventory lists 14 servers and network devices, including one forgotten science department server.
Synthetic case. The school and devices are synthetic.
Errors and limits
Assuming devices like printers need no updates leaves known weaknesses on busy networks.
Exercises
- EX001 — Firmware devices. Why do printer and projector firmware matter for network security?
Show marking criteria
Rubric: 3 = run outdated firmware on shared network, could be misused;; 2 = outdated;; 1 = not relevant;; 0 = none. - EX002 — Service description. How should a system be described for writing network rules?
Show marking criteria
Rubric: 3 = by services offered, ports and clients served;; 2 = services;; 1 = hardware;; 0 = none. - EX003 — Forgotten server. What did the inventory reveal in the science department?
Show marking criteria
Rubric: 3 = forgotten data-logging server on student network;; 2 = old server;; 1 = vague;; 0 = none.
Synthesis
Knowing what systems exist and what services they offer is the starting point for network security.