Networking & Security Foundations covers: Head First Networking, Web Penetration Testing with Kali Linux, Cybersecurity Attack and Defense Strategies. Understand TCP/IP, DNS, HTTP, TLS, firewalls, and basic security concepts. Know what happens between the browser and your Rails app at every network layer.
Every Rails app is a networking application. Rack sits on top of TCP. ActionCable uses WebSockets. ActiveStorage uploads to S3 over HTTPS. Devise handles authentication over TLS. When your health check fails, is it the app or the network? When SSL certificates expire at 3 AM, do you know how to renew them? When your app is slow, is it the database query or the network latency between app server and database?
| Rails Situation | Networking Skill |
|----------------|-----------------|
| SSL certificate expired | TLS, openssl s_client, cert renewal |
| DNS propagation delay | dig, TTL, DNS resolver caching |
| Load balancer health check fails | HTTP status codes, TCP connections |
| WebSocket connections dropping | TCP keepalive, proxy timeouts |
| CORS errors | HTTP headers, preflight OPTIONS |
This course unlocks once you've finished its prerequisite. Open prerequisite →
TCP/IP will feel academic for the first few days. Layers, packets, handshakes, routing tables -- it reads like a networking textbook because it is one. And then one day you will b…
Every incident starts with the same three words: "the app's down." That sentence contains almost no information — and the whole discipline of this course is turning it into a spec…
Somebody is going to read your application looking for the query you forgot to scope to currentuser, the parameter you trusted, the endpoint you left without authorization. The on…
The previous lesson taught you to find the hole and patch it. This one asks a harder question: how do you build a system where a single missed hole doesn't end in a breach? Fixing…
Work through each item before the checkpoint.
Use tcpdump or Wireshark to capture a full HTTP request to your Rails app. Annotate every packet: DNS query, TCP handshake, TLS negotiation, HTTP request, HTTP response, TCP teard…
6 lessons. Read in order; spiral back when you need to. By the end you'll have used the core ideas twice — once on the abstract, once on something you'll meet at work next week.