
# Log4Shell: My Journey Building an Advanced Rust Scanner

Hey there, fellow code wranglers and security enthusiasts! It's YEZZFUSL here, and boy, do I have a story for you. Remember the chaos when Log4Shell hit the fan back in 2021? Yeah, that was a fun weekend, wasn't it? (Spoiler: It wasn't.)

## The Log4Shell Nightmare

So there I was, enjoying my Friday night pizza when my phone blew up with alerts. CVE-2021-44228 had just dropped, and it was bad. Like, "pour coffee directly into your servers to stop them from catching fire" bad.

For those who mercifully blocked that memory, Log4Shell was a vulnerability in Log4j that basically let attackers tell your Java app, "Hey, go fetch and run this totally-not-malicious code for me, pretty please?" And because Log4j is in everything (seriously, I found it in my toaster), it was a global "oh crap" moment.

## From Panic to Project

After the initial firefighting (and a lot of caffeine), I started thinking. We patched our stuff, sure, but how could we be certain we caught everything? That's when my weekend project was born: a scanner to find this sneaky bug.

Why Rust, you ask? Well, I had been meaning to learn it, and nothing motivates like a good crisis, right? Plus, I figured if I was going to lose sleep over this, I might as well gain a new skill.

## Building the Beast

My initial scanner was pretty basic - just grep with extra steps. But as I dug deeper into the weird and wonderful ways Log4Shell could hide, I realized we needed something smarter. Here's how it evolved:

1. **Multi-threading**: Because scanning one file at a time is so 2010.
2. **Fancy Hashing**: SHA-256, SHA-3, Blake3 - like Pokemon, gotta catch 'em all.
3. **Entropy Analysis**: Turns out, malicious code often looks as random as my first attempts at Rust syntax.
4. **Fourier Transform**: Because nothing says "overkill" like using signal processing to find vulnerabilities.
5. **Markov Chains**: I may have gone too deep down the rabbit hole at this point.

## The "Aha!" Moments

Building this scanner taught me more than just Rust. Here are some nuggets of wisdom I picked up:

1. **Java is everywhere**: I found Log4j in places I never expected. It's like glitter - once it's in your environment, you'll never get rid of all of it.

2. **Obfuscation is an art**: Some of the ways people tried to hide Log4Shell were genuinely impressive. Evil, but impressive.

3. **Performance matters**: When you're scanning terabytes of data, every millisecond counts. Rust's speed was a lifesaver.

4. **False positives are the worst**: My early versions had more false alarms than a paranoid smoke detector. Tuning is crucial.

## The Results

After weeks of coding, debugging, and questioning my life choices, the scanner was ready. And you know what? It worked pretty darn well. We found several instances of Log4Shell that had slipped through our initial pass.

But the real win? I now had a flexible, fast, and frighteningly over-engineered tool for future vulnerability hunts. Plus, I could finally add "Rust developer" to my Twitter bio. Dreams do come true!

## Lessons Learned

If there's one thing I want you to take away from this, it's this: security is a never-ending game of cat and mouse. Today it's Log4Shell, tomorrow it'll be something else. Stay curious, keep learning, and for the love of all that is holy, patch your systems!

Oh, and if you're curious about this Lovecraftian horror of a scanner I've created, check it out on my GitHub. Feel free to use it, improve it, or just laugh at my code comments. We're all in this together!

Stay safe out there, and remember: in the world of cybersecurity, paranoia is just another word for "job security."

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Want to see the monster for yourself? Check out the [RustyLog4jGuard CVE-2021-44228 Scanner on GitHub](https://github.com/yezzfusl/RustyLog4jGuard). Don't worry, it doesn't bite... much.
