binwalk -e firmware.bin && grep -r "password" ./_firmware.bin.extracted/
When you run this command and see that clear-text 'root:admin123' line, it’s proof of how a billion-dollar infrastructure can hang by a very thin thread. In the IoT (Internet of Things) world, things don't work like web apps hidden behind fancy firewalls. Here, the rules are harsh, resources are limited, and mistakes usually echo in the physical world.
On our side—during Red Team operations—the first thing we do when we encounter an IoT device is to extract its 'soul.' That block of software we call firmware is actually a black box containing all the device's secrets. But most manufacturers forget to close the lid.
Firmware Analysis: Opening the Box
Think about a scenario we encountered in a field project at testCompany. We have an IP camera or an industrial sensor. The first step is to either download the firmware from the manufacturer's site or dump it from the SPI flash chip on the device. When we slice this firmware open with binwalk, we usually find a miniature Linux distribution staring back at us.
This is where the real fun begins. Most developers leave 'backdoor' accounts or test API keys used during the development phase inside the production firmware.
Imagine the contents of a sample etc/shadow file:
root:$1$vG$7f8...:18234:0:99999:7:::
admin:$1$xy$2a1...:18234:0:99999:7:::
Cracking these hashes sometimes takes only a few seconds with today's GPU power. If you don't want to bother with hash cracking, a quick tour through the file system with grep might give you much more:
# Defanged/Harmless Example
grep -ri "api_key" .
grep -ri "aws_secret" .
grep -ri "mqtt_pass" .
MQTT: The Silent Killer of Security
MQTT is the favorite protocol for IoT devices to talk to each other. It’s lightweight and fast, but if not configured correctly, it’s a total disaster. In many setups, 'Authentication' is turned off, or everyone is allowed to subscribe to every topic.
Suppose an attacker has breached the network and starts listening to the MQTT broker at test-broker.example.com:
# Defanged Python/Paho-MQTT Listener Example
import paho.mqtt.client as mqtt
def on_message(client, userdata, message):
print(f"Topic: {message.topic} | Data: {message.payload.decode()}")
client = mqtt.Client("Pentest_Scanner")
client.connect("127.0.0.1", 1883) # Local mock IP
client.subscribe("#") # Subscribe to all topics (Wildcard)
client.on_message = on_message
client.loop_forever()
Thanks to the # wildcard character, this simple script dumps all sensor data, door lock statuses, and sometimes even user passwords onto the screen. In real life, this data could include critical temperature thresholds for a factory or the command to open a smart lock.