DEV Community

Cover image for How to Build India's Cheapest (Yet Most Effective) Penetration Testing Tool 🔥
Nitin Kumar
Nitin Kumar

Posted on

How to Build India's Cheapest (Yet Most Effective) Penetration Testing Tool 🔥

#cybersecurity #arduino #badusb #securitytesting

Introduction

Hey there, cyber warriors! Ever wondered how security researchers make those jaw-dropping demos where a simple USB stick can bring down an entire network? Well, buckle up because today we're diving deep into the world of HID (Human Interface Device) attacks using none other than the legendary Digispark ATTiny85 – your ticket to penetration testing glory without burning a hole in your pocket! 💸

In a country where we're masters at making the most with the least (जैसे कि मुंबई में 10 फ़ुट के कमरे में 5 लोग रहना), it shouldn't surprise you that we can build a professional-grade pentesting tool for less than the price of a decent Dosa! 😂

Let's get started with this mind-blowing journey of turning a ₹350 chip into a security professional's secret weapon!

Objective

Our main objective here (drumroll please 🥁) is to create an affordable, stealthy HID device that mimics a wireless mouse/keyboard dongle capable of executing pre-programmed attacks autonomously upon insertion. Think of it as your personal digital jadoo (magic) that works as soon as it touches the target system.

🎯 Specific Goals:

  • Build a functional HID attack device under ₹500
  • Make it appear as a legitimate wireless mouse dongle
  • Execute automated payload sequence: wake system → open browser to specific URL → close browser → execute shutdown command
  • Ensure device maintains HID functionality post-attack (for stealth)
  • Keep everything undetected by traditional antivirus solutions (because who doesn't love flying under the radar? 🦅)

Hardware Requirements

Remember how we said we're going budget-friendly? Well, here's where we prove it! 🤑

Main Hardware (The Hero of Our Story):

This little beauty is cheaper than your monthly chai consumption but more dangerous to unpatched systems! 💻💥

Optional Accessories (Because We Like to Dress Up Our Toys):

  1. USB Enclosure/Case – ₹100-200 (To make it look fancy like those premium wireless mouse dongles)
  2. USB Extension Cable – ₹50 (For harvesting those components, just like mom uses empty containers 🥡)
  3. Breadboard Jumper Wires (if not included) – ₹30
  4. Soldering Kit (If you're feeling extra DIY) – ₹200-500 [Local Electronics Store]

💡 Pro Tip: You can always salvage components from old USB devices lying around. Remember, in Indian households, nothing goes to waste! 🏠🗑️

Other Alternatives (For Those Who Want to Spend More 💸):

But why spend more when you can build the same thing for less? As they say, "सस्ता सोना चाँदी से भी चमकदार होता है!"

Software Requirements

Let's get our digital workspace ready – it's time to install some serious stuff!

Arduino IDE (The Boss Software) 👑:

Absolutely free and open-source! No excuses for not downloading this:

🔗 Download Link: https://www.arduino.cc/en/software

It's like downloading WhatsApp but for hardware hackers!

Digistump Board Package (The Magical Add-on):

Don't worry, no magic wand required, just some simple copy-pasting! Follow these steps:

  1. Open Arduino IDE
  2. Go to File → Preferences
  3. In "Additional Boards Manager URLs" field, paste: http://digistump.com/package_digistump_index.json
  4. Click OK
  5. Go to Tools → Board → Boards Manager
  6. Search for "Digistump"
  7. Install "Digistump AVR Boards by Digistump"

💡 This is like adding a new channel to your TV – suddenly you can see way cooler content!

How To: The Complete DIY Guide 🛠️

Step 1: Assembling Hardware (Or Not Assembling, Depending on Your Mood)

The beauty of the Digispark (yes, there's beauty in simplicity!) is that it comes pre-assembled. You just need to plug it in... well, almost!

But if you're feeling fancy and want to make it look like a premium wireless mouse dongle, here's the plan:

  • Option 1: Plug & Play – Just use the existing micro-USB connector. Fast, easy, no soldering required. Perfect for those who hate DIY with a passion!

  • Option 2: Stealth Mode (काला घोड़ा अंधेरे में दौड़ता है):

    1. Desolder the micro-USB connector (if you're brave enough 🤯)
    2. Salvage an old USB-A male connector (from a broken mouse or an extension cable)
    3. Solder wires directly to the ATTiny85 chip:
      • VCC → 5V
      • GND → GND
      • D+ → Pin 3
      • D- → Pin 4
    4. Enclose everything in a nice USB-shaped case
    5. Add some hot glue for that premium waterproof feel! 😎

Step 2: What Will We Do Exactly?

Here's the evil plan (but a very authorized one!):

  1. Device wakes up the sleeping computer (because we're polite like that 😇)
  2. Automatically opens a browser to visit your specified website
  3. Closes the browser (keeping things clean like our moms taught us!)
  4. Opens Command Prompt (CMD)
  5. Executes a shutdown command with a 60-second countdown
  6. Maintains mouse functionality so it looks like a genuine wireless mouse dongle (nobody suspects the cute little mouse!)

Step 3: The Payload – What Makes This Device Dangerous 😈

Here's the exact code that will bring tears to a system administrator's eyes:

#include "DigiKeyboard.h"

void setup() {
  DigiKeyboard.delay(3000);
  DigiKeyboard.sendKeyStroke(0); // Initialize
  DigiKeyboard.delay(100);

  // Wait for system to fully wake up
  DigiKeyboard.delay(3000);

  // Open Run dialog
  DigiKeyboard.sendKeyStroke(KEY_R, MOD_GUI_LEFT);
  DigiKeyboard.delay(500);

  // Launch Chrome/Edge with the specified URL
  DigiKeyboard.print("chrome.exe https://nitinkumar30.netlify.app/");
  DigiKeyboard.sendKeyStroke(KEY_ENTER);
  DigiKeyboard.delay(8000);

  // Close browser
  DigiKeyboard.sendKeyStroke(KEY_F4, MOD_ALT_LEFT);
  DigiKeyboard.delay(1000);

  // Open CMD
  DigiKeyboard.sendKeyStroke(KEY_R, MOD_GUI_LEFT);
  DigiKeyboard.delay(500);
  DigiKeyboard.print("cmd");
  DigiKeyboard.sendKeyStroke(KEY_ENTER);
  DigiKeyboard.delay(1000);

  // Execute shutdown command
  DigiKeyboard.print("shutdown /s /t 60");
  DigiKeyboard.sendKeyStroke(KEY_ENTER);
}

void loop() {
  // Nothing to do here (single shot attack)
}
Enter fullscreen mode Exit fullscreen mode

💡 Understanding the Payload:

  • DigiKeyboard.delay() – Gives system time to process actions
  • sendKeyStroke(KEY_R, MOD_GUI_LEFT) – Equivalent to pressing Windows Key + R
  • DigiKeyboard.print() – Types text characters
  • MOD_ALT_LEFT / MOD_GUI_LEFT – Modifier keys (Alt, Windows key)

Step 4: Instructions to Upload Payload (The Moment of Truth!) ⚡

  1. Open Arduino IDE – Make sure you've installed the Digistump package as discussed earlier
  2. Select Board Settings:
    • Go to Tools → Board → Select "Digispark (Default - 16.5mhz)"
  3. Paste Your Payload Code – Copy-paste the code from above into the IDE
  4. Click Verify – Make sure there are no compilation errors. If there are, double-check your typing (we've all been there! 👀)
  5. Click Upload – This is where things get interesting!
  6. NOW (and only NOW) plug in your Digispark – This device uploads code when connected, not before!
  7. Watch for the success message: "Micronucleus done. Thank you!" (It's like the device is saying "thanks for making me dangerous!")

⏰ Important Timing Tip: You have 60 seconds after clicking upload to plug in the device. Set an alarm if you're prone to forgetting! ⏰

Testing & Deployment (The Fun Part!) 🎯

Before unleashing this digital beast on actual targets (with proper written permissions, of course!), let's test it safely:

Safe Testing Protocol:

  1. Prepare a test computer (one you own or have explicit permission to test)
  2. Save all work (no one likes losing data!)
  3. Plug in your Digispark and watch the magic unfold 🎩✨
  4. If shutdown command executes, quickly cancel it by typing shutdown /a in CMD

Deployment Tips:

  • The device maintains HID functionality post-attack, so it appears as a legitimate mouse even after the payload execution
  • Most systems don't have USB-based antivirus scanning for HID devices (which is why this method works so well!)

💡 Security Pro Tip: This attack is so effective because it bypasses traditional antivirus detection. AVs are looking for malicious files, not legitimate keyboard inputs!

Why This Method Works Like Magic ✨

Undetectable & Stealthy:

  • Appears as Standard HID Device – Your Digispark looks like any other USB mouse or keyboard to the system
  • No File Write Required – Unlike USB drives, this device doesn't mount as storage, so it can't be scanned by file-based antivirus
  • Keyboard/Mouse Input – Antivirus won't flag you for typing "shutdown /s" because, technically, that's what it looks like to the system
  • Physical Appearance – With proper casing, it literally looks like a wireless mouse dongle, making it completely innocuous in appearance

As they say, the best hiding place is in plain sight! 🙈

Legal & Ethical Reminder (Read This Before Getting Overconfident!) ⚠️

🚨 SERIOUS BUSINESS SECTION – PLEASE READ CAREFULLY 🚨

This technique is EXTREMELY powerful and should only be used in authorized penetration testing scenarios with:

  1. Written permission from the system/network owner
  2. Proper documentation and approval from relevant authorities
  3. Compliance with IT Act 2000 (India) and similar regulations elsewhere
  4. Responsible disclosure practices if vulnerabilities are found

❌ DON'TS:

  • Don't plug this into random public computers (like in cyber cafes)
  • Don't use it to prank friends (trust us, they won't find it funny when their computer shuts down)
  • Don't test on systems you don't own without explicit written permission
  • Don't lose your job/face legal consequences because you thought this was a joke 😅

✅ DOs:

  • Use in authorized pentesting engagements
  • Document all testing activities
  • Follow responsible disclosure practices
  • Educate organizations about USB security risks

Summary

Let's wrap this up faster than a shutdown command executes! 😂

We've learned how to:

  • Build a professional-grade HID attack device for under ₹500 💰
  • Make it appear absolutely legitimate as a wireless mouse dongle 🖱️
  • Program it to execute automated payloads without file-based antivirus detection 🛡️
  • Understand the technical aspects while keeping costs minimal 📉

Key Takeaways:

  1. Cost-Effective: ₹350 hardware gives you professional capabilities
  2. Undetectable: Appears as legitimate HID device
  3. Autonomous: Executes attacks without user interaction
  4. Reusable: Can be reprogrammed for different payloads
  5. Stealthy: Maintains mouse functionality for disguise

The Digispark ATTiny85 is like the "Aam Aadmi" of penetration testing hardware – affordable, accessible, and shockingly effective! Whether you're a security professional, researcher, or hobbyist, this device proves that sometimes the cheapest solution is the most powerful one.

So go ahead, build your own, test responsibly, and remember – with great power (and cheap hardware) comes great responsibility! 👨‍💻✨

And hey, if this article helped you, you know what to do – smash that like button! (Just kidding, there's no like button, but you get the point 😂)

Top comments (0)