EP 11: Think Like a Hacker

#security

The Developer Blindspot: The "UI Facade"

Most developers test their APIs through the lens of the frontend they built. They assume that because the React form has a max-length attribute or a dropdown with fixed values, the backend will only ever receive those values.

This is a critical oversight. A hacker doesn't use your UI. They treat your frontend like a facade that can be ignored. To build truly resilient systems, you must stop testing like a user and start testing like an adversary.

Enter Burp Suite: The Intercepting Proxy

Burp Suite is the industry-standard tool for web security auditing. At its core, it acts as an Intercepting Proxy. It sits directly between your browser and your server, acting as a man-in-the-middle.

When you click a button in your app, Burp "pauses" the request. It holds the data in limbo, allowing you to inspect, modify, and replay that request before it ever touches your server.

Testing Your Architecture: 3 Common Attacks

1. The "Price Manipulation" Test (Logic Flaws)

This is the classic "check-out" vulnerability.

The Scenario: You are building an e-commerce platform. The UI displays an item for $100.
The Attack: You click 'Buy.' Burp catches the POST request. You see {"itemId": "pro-123", "price": 100}.
The Modification: You change 100 to 1 and hit "Forward."
The Result: If your backend processes that order for $1, you have a massive logic flaw. You trusted the client-side "source of truth" instead of verifying the price against your database on the server.

2. IDOR: Can I See My Neighbor's Data?

Insecure Direct Object Reference (IDOR) occurs when a system provides access to objects based on user-supplied input.

The Attack: You log in and see your profile at /api/users/v1/555.
The Modification: In Burp Repeater, you change that ID to 556, 557, or 558.
The Goal: If the server returns the private data of other users without checking if you own that record, your authorization logic is broken.

3. Mass Assignment: Upgrading Your Own Permissions

Imagine a registration or profile update endpoint.

The Attack: You send a request to update your username: {"username": "hrishi_dev"}.
The Modification: You "guess" internal field names and add them to the JSON body: {"username": "hrishi_dev", "isAdmin": true, "balance": 99999}.
The Result: If your backend blindly spreads that object into your database (e.g., db.user.update({...req.body})), you’ve just allowed a user to escalate their own privileges.

Why Every Developer Needs a Security Mindset

Using Burp Suite isn't just for Pentesters; it's a vital part of a modern System Design workflow.

Visibility: You see the "naked" request—every header, cookie, and hidden metadata field. You realize how much information your app is actually leaking.
Zero-Trust Architecture: It forces you to adopt a "Zero Trust" policy toward the client. You begin to treat every incoming request as potentially malicious.
Better Validation: Once you see how easy it is to bypass a frontend regex, you start implementing robust schema validation (like Zod) on the backend.

The Takeaway

Your system's security is not defined by how well your UI works; it's defined by how your API handles a "broken" request. By using tools like Burp Suite to audit your own work, you catch vulnerabilities in the development phase—long before a real attacker finds them.

Pro-Tip: Start with Burp Suite Community Edition. Use the Repeater tool to modify and re-send requests without having to refresh your browser. It’s the fastest way to debug and secure your API logic simultaneously.