Password Checker

Preston P — Wed, 15 Jul 2026 21:50:43 +0000

Building a Password Checker: Strength + Breach Detection in Python

I recently built my second cybersecurity tool — a password checker that does two things: analyzes password strength AND checks if it's been leaked in a data breach. Here's how I built it.

The Inspiration

After building my first tool (a multi-threaded port scanner), I wanted to tackle something directly related to everyday security. Passwords are everywhere, and most people don't know if their passwords are strong or if they've been exposed in a breach.

I wanted to build a tool that would answer two questions:

Is this password strong?
Has this password been leaked?

What It Does

🔐 1. Strength Analysis

The tool checks five criteria and gives a score from 0-6:

Criteria	Points
Length (12+ characters)	+2
Length (8-11 characters)	+1
Uppercase letters	+1
Lowercase letters	+1
Numbers	+1
Symbols (!@#$%^&*)	+1

Score Interpretation:

Score	Rating
5-6	🟢 GREAT
4	🟢 GOOD
3	🟡 DECENT
0-2	🔴 WEAK

🛡️ 2. Breach Detection

The tool checks the HaveIBeenPwned API to see if your password appears in any known data breaches.

How it stays secure:

Your password is never sent over the internet
Only the first 5 characters of the SHA-1 hash are sent
This is called k-anonymity — the API never sees your full password

Conclusion
Building this password checker taught me a lot about:

Working with APIs

Cryptographic hashing

Privacy-first design

Creating useful, user-friendly tools

If you're learning cybersecurity or Python, I highly recommend building tools like this. You learn far more than you would from following tutorials alone.

This is my second cybersecurity project. If I can build it, so can you. 🚀

Port scanner Project

Preston P — Thu, 09 Jul 2026 04:26:20 +0000

Building My First Cybersecurity Tool:

A Multi-Threaded Port Scanner in Python

A few weeks ago, I didn't know what a port was. Today, I built a tool that can scan 1,000 ports in under 10 seconds. Here's how I did it.

The Backstory

I'm a high school student interested in cybersecurity, and I wanted to build something real. Not just follow a tutorial, but actually create a tool from scratch.

I decided to build a port scanner because:

It's a fundamental cybersecurity tool
It would teach me networking basics
I could use what I learned in Python class (AP CSP)
I wanted something to put on my GitHub

This is what I built:

** What Is a Port Scanner?**

Think of a computer like a huge apartment building with 1,000 numbered doors (ports). Each door leads to a different service:

Port	Service
80	Websites (HTTP)
443	Secure websites (HTTPS)
22	Remote access (SSH)
3306	Databases (MySQL)

A port scanner "knocks" on each door to see which ones are open. If a door is open, there might be a service running that could be a security risk (or just something useful!).

Conclusion
Building this port scanner taught me more than any textbook could. If you're interested in cybersecurity, I highly recommend building your own tools — it's the best way to understand how things actually work.

Thanks for reading! Feel free to ask questions or suggest improvements.

DEV Community: Preston P