Firewall Types
Packet, stateful, and app firewalls.
Firewall Types is a free Cyber Security Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Cyber Security Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What Is a Firewall
A firewall is a security barrier that controls traffic between networks.
It decides which packets are allowed through and which are blocked, based on a set of rules.
Why Firewalls Matter
Without a firewall, any device on the internet could try to reach your systems directly.
A firewall is the first line of defense, separating trusted internal networks from untrusted external ones.
Packet Filtering Firewalls
The simplest type is the packet filter. It inspects each packet's basic header fields.
- Source and destination IP
- Source and destination port
- Protocol (TCP, UDP, ICMP)
Stateless Decisions
A pure packet filter is stateless. It judges each packet on its own, with no memory of past packets.
This is fast but cannot tell if a packet belongs to an existing, legitimate conversation.
Stateful Firewalls
A stateful firewall tracks active connections in a state table.
It remembers that you started a connection, so it can automatically allow the matching reply traffic back in.
Why State Helps Security
Because it understands connections, a stateful firewall can reject packets that pretend to be replies to a conversation that never happened.
This blocks many spoofing and scanning tricks that fool stateless filters.
Application Layer Firewalls
An application firewall (proxy firewall) understands specific protocols like HTTP.
It can inspect the actual content, not just headers, blocking malicious requests inside otherwise valid traffic.
Web Application Firewalls
A WAF is a specialized application firewall for web apps.
It defends against attacks like SQL injection and cross-site scripting by examining web requests before they reach the server.
Next-Generation Firewalls
A next-generation firewall (NGFW) combines many capabilities in one device.
- Stateful filtering
- Application awareness
- Intrusion prevention
- Threat intelligence feeds
Host vs Network Firewalls
Firewalls run in two places:
- Host firewall - software on a single device
- Network firewall - protects an entire network at its edge
Good security uses both together.
Hardware and Cloud Firewalls
Firewalls can be physical appliances, software, or cloud services.
Cloud providers offer security groups and managed firewalls that protect virtual machines and services without any physical hardware.
Quick Check
Test your understanding of firewall types.
Recap
Firewall types include:
- Packet filtering - stateless, header-based
- Stateful - connection-aware
- Application / WAF - content-aware
- NGFW - all-in-one
Layering host and network firewalls strengthens defense.
Frequently asked questions
Is the “Firewall Types” lesson free?
Yes — the full text of “Firewall Types” is free to read here on the web, and the Cyber Security Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Cyber Security Academy course, upgrade to CoddyKit PRO.
What will I learn in “Firewall Types”?
Packet, stateful, and app firewalls. You practise Cyber Security Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Cyber Security Academy?
No prior experience is required. Cyber Security Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Firewall Types” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Cyber Security Academy lesson?
Yes. Every Cyber Security Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Firewall Types
- Rules and Policies
- Network Segmentation
- DMZ Design