IT Fundamentals & Security: interview questions and learning guide

Networking basics

The postal system of the internet: addresses, sorting offices and roads.

Devices on a network are identified by IP addresses. DNS turns names into addresses, routers move traffic between networks, firewalls filter it, and VPNs protect it over the internet.

Interview tip: Explain with the postal analogy: address, sorting, delivery.

Cloud basics

Renting electricity instead of owning a power plant.

Cloud providers rent computing over the internet. IaaS gives raw servers, PaaS gives a platform to run apps, and SaaS gives finished software. You pay for what you use and can scale up or down quickly.

Interview tip: Know the difference between IaaS, PaaS and SaaS by heart.

Cybersecurity basics

Locks, guards and alarms for your digital house.

Security protects people, data and systems. Most attacks start with people, such as phishing, so training matters. Layers like multi-factor sign-in, encryption and regular patching reduce the damage of any single failure.

Interview tip: Say layers: no single control is enough.

Operating systems

The operating system is the manager of a hotel who gives rooms, keys and services to every guest.

An operating system sits between hardware and applications. It runs processes, shares the processor among them, manages memory, stores files and controls devices through drivers. It also handles users, permissions and updates. Windows, Linux and macOS differ in design but share these jobs. IT support staff need to read the task manager, fix boot problems, manage users and apply updates safely.

Interview tip: Explain what happens from pressing the power button to seeing the login screen in five clear steps.

DNS, DHCP and subnetting

DNS is the phone book, DHCP is the receptionist giving out desk numbers, and a subnet is one floor of the building.

Devices on a network need an address, a way to find names and a way out to other networks. DHCP hands out an IP address, mask, gateway and DNS server automatically. DNS turns names like a website into IP addresses. A subnet mask splits an address into a network part and a host part, and CIDR writes it as a slash number. Tools such as ping, nslookup and traceroute help you find where a connection breaks.

Interview tip: Learn to calculate usable hosts for a slash 24 and a slash 26 quickly, since subnetting is a favourite test.

Cloud services: IaaS, PaaS, SaaS, storage and IAM

Cloud is renting power and storage like electricity, instead of building your own power plant.

Cloud providers rent computing by the hour. In infrastructure as a service you manage the server, in platform as a service you manage only your app, and in software as a service you just use the product. Storage comes as objects, blocks or files, each for different needs. Identity and access management decides who can do what, and the shared responsibility model says the provider secures the cloud while you secure what you put in it.

Interview tip: Describe one service for each model and say who patches the operating system in each case.

Cybersecurity threats and defences

Security is a castle with a moat, walls and guards: one layer alone is never enough.

Attackers use malware, phishing, weak passwords, unpatched software and web flaws. Common attacks include ransomware, denial of service, injection and man-in-the-middle. Defence works in layers: patching, strong authentication, firewalls, endpoint protection, backups, monitoring and staff training. When something goes wrong, a clear incident response process limits damage. The most successful attacks still target people, so awareness matters as much as tools.

Interview tip: Show you know the order of incident response: contain first, then investigate, then recover.

ITIL and service management

Service management is running IT like a good restaurant: clear menu, promised timings and steady improvement.

ITIL is a framework of good practices for delivering IT as a service. It is built around value: the work the business needs, not just the technology. Practices such as incident management, problem management, change enablement and service request management have clear roles and goals. Service levels set agreed targets, and continual improvement keeps raising quality. Most service desks and ITSM tools such as ServiceNow follow these ideas.

Interview tip: Be able to separate an incident, a problem, a change and a service request with one line each.

DevOps and CI/CD

DevOps is a relay team where developers and operations pass the baton smoothly instead of throwing it over a wall.

DevOps joins development and operations so software ships faster and safer. Continuous integration merges and tests code often, and continuous delivery keeps every build ready to release. A pipeline automates build, test and deploy steps. Containers package an app with its needs, and infrastructure as code builds servers from files. Monitoring and logs close the loop so teams learn from real use.

Interview tip: Describe one pipeline you have built or read, stage by stage, even if it was a small project.

Contain it, investigate and block the sender, reset affected passwords, check logs and raise awareness.

DNS finds the IP address, the browser sends a request, the server responds and the browser renders the page.

The browser asks DNS for the IP address, opens a TCP and TLS connection, sends an HTTP request, the server replies with the page and the browser renders it.

TCP is connection based and reliable, with ordering and retransmission. UDP is faster with no guarantee, used for video calls and DNS.

Check the device Wi-Fi switch, other devices on the network, the router, IP address and DNS, forget and rejoin the network, then update drivers or escalate.

DHCP automatically gives devices an IP address, subnet mask, gateway and DNS server, so nobody sets them by hand.

A Microsoft directory service that stores users, groups and computers and controls login and permissions across a company network.

A virus spreads by attaching to files. Ransomware encrypts your data and demands payment. Defence is backups, updates and careful email habits.

RAID 0 stripes for speed with no safety, RAID 1 mirrors two disks, RAID 5 stripes with parity and survives one disk failure.

Verify the user identity by policy, use the self-service or admin reset, force a password change at next login and log the ticket.

DNS finds the IP address, the browser opens a connection, sends an HTTP request, the server replies and the browser shows the page.

A switch connects devices inside one network. A router connects different networks and sends traffic between them, such as your home and the internet.

A service that gives devices an IP address and network settings automatically when they join a network.

Check the device Wi-Fi is on, the right network and password, other devices, signal, IP address and the router. Then restart and escalate if needed.

A way to combine disks for speed or safety. For example RAID 1 mirrors data so one disk can fail without data loss.

A backup is a saved copy for restore later. Replication keeps a live copy in sync for quick failover, but also copies mistakes.