How Hackers Are Hiding Dangerous Code in Images—And Why You Should Care

It might sound like something out of a spy movie, but cybercriminals are actually hiding harmful code inside images—and it's becoming a serious problem.

This trick isn’t new, but black hat hackers are constantly evolving. They’ve found clever ways to slip malicious code into places you’d never suspect: email attachments, PDFs, Excel sheets, and now, even innocent-looking JPG or PNG files. It could be a picture of a cat—or something far worse under the surface.

The scary part? These techniques are getting easier to use and harder to detect. Hackers use methods like steganography—a way of hiding data in plain sight—and tools that modify tiny, almost invisible bits of the image’s code to smuggle malware past your defenses.

With this, they’re spreading nasty programs like Keylogger, 0bj3ctivityStealer, and Lumma Stealer—tools specifically built to steal your personal info, track what you type, or quietly spy on your computer without you ever knowing.

According to the HP Wolf Security Threat Insights Report, these image-based attacks are showing up in phishing emails, on GitHub, and even on trusted sites like the Internet Archive. That’s right—hackers are planting traps in places we usually feel safe.

The real danger lies in how invisible it all is. One click on an image, and your personal or company data could be compromised. It’s unsettling to think a harmless-looking picture could be hiding a threat—but that’s the new reality of cybercrime.

Key Points to Remember:

• Hackers are using images to sneak malware into systems, bypassing traditional security.
• Tools that hide code in image metadata or tweak pixel data are easy to find and use.
• These attacks are spreading through emails, websites, and open-source platforms.
• If infected, the hidden code can steal passwords, spy on users, or deploy damaging malware.

A picture might be worth a thousand words—but these days, it might also carry a silent, hidden threat.

How Hackers Hide Malicious Code in Images — And Why It’s So Hard to Spot

It’s unsettling to think about, but some of the most dangerous cyberattacks today are hiding in plain sight — inside innocent-looking images. Yes, something as ordinary as a photo you download or see online could be harboring hidden malicious code, thanks to a sneaky trick hackers use.

Let’s break down how these cybercriminals actually pull this off.

1. Choosing the “Perfect” Image

Before anything else, hackers need the right image. This isn’t just any picture — it has to look harmless. Think of a typical JPEG or PNG that wouldn’t raise an eyebrow. But underneath that normal-looking exterior, there could be trouble.

For example, if the goal is a phishing email, the image might be a logo or a common email banner. If it's a phishing website, they may choose images that blend in with what you’d expect to see on that kind of site.

Malicious code smuggled inside an image can trigger downloads of more scripts. Source: HP Wolf

And they’re crafty — some hackers have even used innocent images hosted on trustworthy platforms like GitHub or the Internet Archive to carry out their plans. In one case, an image was discovered that quietly triggered the download of a second, more dangerous image — all without the user knowing.

It’s a chilling reminder of how creativity in the wrong hands can become a weapon.

2. Using Steganography Tools to Hide the Code

Once the image is selected, hackers use a technique called steganography — basically, the art of hiding things in plain sight. There are tools out there (many freely available online) that allow data to be buried deep inside image files without changing how they look.

To the naked eye, it’s just a normal picture. But within the pixels, there could be a payload of harmful code waiting to strike.

Skilled hackers sometimes go a step further, building their own tools from scratch using languages like C++ or Java, or even modern AI. It’s not just technical — it’s personal. These hackers take pride in crafting something that’s nearly impossible to detect.

3. Clever Encoding Tricks: Metadata and Pixel Manipulation

There are a couple of ways hackers hide their code inside images:

• Metadata: This is the hidden info that’s stored in every image file — things like when the picture was taken or the camera used. Hackers can stuff malicious scripts in here without touching the actual visual content.
• Least Significant Bits (LSB): This is the sneaky one. Hackers change just a few bits of the image’s pixel data — so small and subtle that the human eye can’t see the difference. But the computer can, and that’s all it takes to unleash the attack.

The goal? Keep the image looking exactly the same, while turning it into a secret delivery system.

4. Linking the Image to a Bigger Attack

The image itself doesn’t always carry the full malware. Often, it’s just the first domino to fall.

Once it’s opened or processed, it may quietly download more malicious files or connect to external servers controlled by the attackers. These files can include things like keyloggers (which record everything you type) or spyware that watches what you do.

Some images even take advantage of old software bugs to run scripts without you ever clicking a thing. In one case, hackers exploited a well-known vulnerability in Microsoft Office just by embedding the right code in an image.

They test these images carefully — making sure they don’t just work, but also look safe.

That’s what makes this technique so dangerous — it blends right into our digital lives.

Screenshot showing a domain analysis for “grassemenwji.shop,” flagged as malicious by security vendors, with a score of 20/94

5. Spreading the Infected Images

Once the weaponized image is ready, the next step is getting it out there. Hackers use all sorts of tricks to do this: phishing emails, fake websites, or even posts on social media.

Sometimes, they upload malicious images to popular sites like GitHub, disguised as part of legitimate-looking software. For example, one hacker uploaded a fake “spoofer” tool — something gamers might use to get around restrictions — and hid the Lumma Stealer malware inside it.

To most users, it seemed like a harmless download. But behind the scenes, it was far from it.

Spoofer software is popular to bypass security controls — but can come with malicious code. Source: Screenshot / Techopedia

What Kind of Tools Do Black Hat Hackers Use to Hide Code in Images?

When it comes to cyberattacks, hackers are always finding sneaky ways to hide their tracks—and sometimes, that means hiding malicious code inside something as innocent-looking as an image.

According to the HP Wolf Security Threat Insights Report, it doesn’t seem like the attackers in a recent campaign used well-known image processing tools like Pillow or pyexiv2. These tools are more common in ethical hacking and general programming; they’re not really built for hiding anything harmful.

Instead, the report points to tools that are specifically designed for hiding data, like:

• Steghide – A classic tool that lets users embed secret data into image files. It’s been around for a while and is pretty effective.
• OpenStego – Another open-source favorite that hides information inside images or even documents.
• Custom Scripts – Some hackers prefer to build their own tools using Python, C++, or other programming languages. That way, they stay under the radar and customize the attack.

To make things even trickier, hackers are now starting to use generative AI to help create malicious code, especially in techniques like HTML Smuggling.

For example, in April 2024, cybersecurity experts at OPSWAT found a piece of malware cleverly hidden inside an image used in an HTML Smuggling attack. It was a chilling reminder of how far these tactics have come.

Now, HTML Smuggling and hiding code in images aren’t exactly the same thing—but they do have a lot in common. Both methods are designed to sneak past security systems and get dangerous code onto a target’s device, all without raising any alarms.

It's a bit unsettling, isn’t it? The same kind of file you’d use to store a vacation photo could be a weapon in the hands of a skilled hacker.

Smuggling code within HTML is another way to get malicious code onto an unsuspecting client. Source: OPSWAT

How Dangerous Can a Simple Image Really Be?

It might sound unbelievable, but even an innocent-looking image can hide something dark beneath the surface. Just by downloading or opening a picture that’s been tampered with, you could unknowingly trigger a chain reaction that leads to a full-blown cyberattack.

Once the hidden malicious code runs, it can quietly install a stealer on your device. And that’s when the real trouble begins.

These stealers are designed to dig deep. They go after everything from your saved passwords and browser cookies to your system data and even the login info for your bank or crypto wallet. It’s like handing over the keys to your digital life without even knowing it.

Worse still, if the image contains spyware, your device could connect to a hacker’s command-and-control (C2) server. From there, the attacker can spy on almost anything—screenshots, keystrokes, audio recordings, live video, even private conversations or meetings. Basically, whatever’s on your device could become theirs.

What makes this all the more frightening is how stealthy these threats are. Modern malware is designed to stay hidden. That means you could be compromised for days or even weeks without a single warning sign—until it’s too late.

Why It Matters

Malicious images aren’t just a tech problem—they're a serious, real-world threat. They can cause massive harm, not just to individuals, but also to companies, governments, and entire organizations.

This technique—hiding harmful code in images—is becoming more popular because it works. It’s quiet, hard to detect, and incredibly effective. Hackers use it to secretly connect your device to their systems, steal data, or drop even more dangerous malware onto your network.

And the scary part? The tools needed to pull this off are everywhere. They’re easy to get, and cybercriminals are getting more creative with how they use them.

From phishing emails to fake websites to booby-trapped downloads, malicious images are becoming a go-to weapon for black hat hackers. And unless we stay alert, this trend is only going to grow.

Final Thoughts

This whole process isn’t just clever — it’s chilling. What makes it so scary is how normal everything looks. A photo. A download. A familiar website.

And yet, underneath, there could be a whole hidden operation designed to steal your data or infect your computer.

It’s a powerful reminder to stay cautious, keep your software updated, and never let your guard down — especially in a world where even a picture might not be what it seems.

FAQs

1. Are malicious images considered zero-click attacks?

Not quite—at least, not yet. Right now, these kinds of attacks still require some level of user interaction. That means the image won’t harm you just by sitting in your inbox or on a webpage. You’d have to open it using vulnerable software, download it, or run it in some way. So while it’s not “zero-click,” it’s still dangerously close—and getting more advanced all the time.

2. Why do hackers bother hiding malware in images?

Because it works. Images—along with files like PDFs, HTML pages, and even innocent-looking JPEGs—are great for sneaking past security systems. Most people don’t think twice about opening an image, and hackers take advantage of that trust. By hiding malware inside something so familiar, they increase the chances you’ll take the bait.

3. How much data can actually be hidden in an image?

Surprisingly, quite a bit. It depends on how big the image is and what steganography technique is used. A skilled hacker can stash a decent chunk of code or sensitive data inside an image without making it look any different. It's like stuffing secrets into a suitcase without leaving a trace on the outside.