Most security problems start long before the first git init. They’re baked into architecture decisions, overlooked assumptions, and missing requirements. Planning is where secure development should start—not because it’s fun, but because it’s cheap. Catching a broken auth model in a whiteboard session is faster than patching a prod breach two sprints later. This section shows you how to design with security in mind from the start. You’ll learn how to run lightweight threat modeling that doesn’t suck, write security-focused user stories, and classify data like a pro. No fluff. No PhD required.

Placeholder image: Image description: Design phase flow with icons for threat modeling, data classification, and secure user story templates—overlaid on a sprint planning board.

Lightweight Threat Modeling for Dev Teams – No PhD or Three-Day Workshop Required

You don’t need to spend days building attack trees or running a threat modeling workshop with 14 stakeholders. You just need to stop and ask the right questions at the right time.

What Could Go Wrong?

This is the question that matters. What happens if a token leaks? If someone tampers with input? If a user bypasses a client-side control? Walk through the basic flows of your feature and poke holes in them. You’re not designing for ideal users—you’re defending against creative abuse. Even 10 minutes of “what if” thinking can catch logic flaws, missing validations, or obvious trust boundaries.

Quick Wins: STRIDE-per-Feature, Whiteboard Sessions

You don’t need to model your entire app. Just threat model the new stuff. Try STRIDE-per-feature. Take five minutes and ask if the feature introduces spoofing, tampering, info leaks, privilege issues, or denial of service. Or grab a whiteboard and sketch the data flow. Who talks to what? Where does user input enter? Where should you have controls? You’ll be surprised how much you catch just by slowing down and drawing lines.

Baking Security into User Stories & Requirements

Security can’t just live in the architecture docs or security team’s backlog. It needs to be part of the dev workflow—starting with how you write stories.

"As a user, I want my data to be..."

User stories are a great place to bake in expectations. Don’t just write “As a user, I want to reset my password.” Try “As a user, I want my password reset to be secure and protected against brute force.” That one sentence triggers rate limiting, token expiration, and logging discussions—before code is written. Security should be part of the definition of done, not an afterthought tacked onto QA.

Data Classification: Knowing What Needs Fort Knox vs. a Simple Padlock

Not all data is created equal. Some fields—like usernames—are public. Others—like SSNs or auth tokens—need encryption, access control, and strict logging. During planning, ask: what data are we collecting? Where is it stored? What’s the impact if it leaks? Label it accordingly. This helps you design protections that match the risk. You don’t need a full-blown data governance strategy to start—just a little labeling and common sense.

Secure development isn’t about stopping innovation. It’s about asking the right questions early, so you don’t have to fix the hard stuff late. 

Let’s move into the code phase and talk about how to write secure logic without turning every pull request into a security incident.