All lessons
Learn how phones and mobile networks actually work. Every lesson comes with a hands-on lab on a simulated phone.
Track 1
Mobile Fundamentals
Start from zero: what's inside, how it talks to towers, how apps are kept apart. Every module runs on a simulated phone, right in your browser.
Course 1: Inside a Phone
What's physically inside the slab in your pocket.
- 1What's InsideTake a phone apart, part by part, on the simulated device.
- 2SensorsThe dozen tiny sensors that let a phone feel the world.
- 3Storage & MemoryRAM vs flash, and why storage is encrypted.
- 4Batteries & ChargingLithium cells, charge cycles and what the port really does.
Course 2: SIMs & Identity
The numbers that identify you and your phone to the network.
- 1The Three NumbersIMEI, IMSI and ICCID, and which one belongs to what.
- 2eSIMA SIM card with no card: how eSIMs get set up.
- 3SIM SwappingHow attackers steal phone numbers, and how to stop them.
- 4Carrier LocksWhy some phones only work on one network.
Course 3: Cellular Networks
How a phone finds a tower and keeps a call alive on the move.
- 1Talking to TowersCells, towers and handing a call off at 60 mph.
- 2Airplane Mode & RadiosFlip the switches yourself and see which radios go dark.
- 32G to 5GWhat actually changed with each generation.
- 4Roaming & CarriersHow your phone works on someone else's network.
Course 4: Wi-Fi & Bluetooth
The short-range radios, and how to use them safely.
- 1Joining Wi-Fi SafelySpot the risky networks in a crowded airport.
- 2Bluetooth BasicsPairing, range and the low-energy beacons all around you.
- 3MAC RandomizationHow phones avoid being tracked by their Wi-Fi address.
- 4NFC & Tap to PayThe 4-centimeter radio behind contactless payments.
Course 5: Mobile Operating Systems
How Android and iOS keep apps in their lanes.
- 1Where App Data LivesEvery app keeps its own files. See where.
- 2PermissionsAnswer real permission prompts and see what you've handed over.
- 3Android vs iOSTwo designs, two security models.
- 4SandboxesThe walls that keep one app from reading another's data.
Track 2
Mobile Networking
Follow your data from the phone to the server and back: packets, DNS, encryption, and exactly who can see what along the way.
Course 1: How Apps Talk
Packets, addresses, DNS and ports: how data finds its way.
- 1Packets & IP AddressesSee how a chat message becomes packets and what an IP address tells you.
- 2DNS: The Internet's Phone BookFollow a DNS lookup from your phone to the server that knows the answer.
- 3Ports & ProtocolsLearn how ports pick the right app and how TCP and UDP differ.
- 4NAT & Your Public IPFind out how many devices share one public IP, at home and on mobile data.
Course 2: Encryption in Transit
How HTTPS keeps your data private on its way to the server.
- 1HTTPS & the PadlockSee how HTTPS protects a connection and what the padlock does and doesn't promise.
- 2Certificates & TrustLearn who vouches for a website and how your phone decides whom to believe.
- 3Certificate PinningSee how some apps trust only their own server's key, and what that costs.
- 4End-to-End EncryptionFind out how some apps lock messages so even their own servers can't read them.
Course 3: Watching Traffic
What others on a network can see, and how to check your own apps.
- 1What an Observer SeesSee what a Wi-Fi owner can and can't learn while you browse over HTTPS.
- 2Intercepting ProxiesRoute your own test phone through a proxy and read what its apps send.
- 3Reading HTTP RequestsLearn to read the parts of an HTTP request and the headers that matter most.
- 4Spotting Leaky AppsSpot the signs of an app that sends too much, or sends it unprotected.
Course 4: Mobile Data Under the Hood
How a phone gets online over cellular, shares it, and stays reachable.
- 1Getting Online Over CellularHow your phone joins the carrier's data network and gets an IP address.
- 2Hotspots & TetheringShare your phone's mobile data with other devices, and learn what that reveals.
- 3IPv6 on PhonesWhy mobile networks moved to IPv6, and how phones still reach IPv4 sites.
- 4How Push Notifications ArriveHow one always-on connection delivers alerts for every app on your phone.
Course 5: Network Privacy
VPNs, encrypted DNS, Private Relay and trackers, minus the hype.
- 1VPNs: What They HideSee what a VPN hides from the local network and who can see your traffic instead.
- 2Encrypted DNSLearn how encrypted DNS hides your lookups and how to turn it on.
- 3iCloud Private RelaySee how Private Relay splits your browsing across two companies, and where it stops.
- 4Trackers & Ad NetworksFind out how apps track you for ads and which phone settings push back.