Blog | G5 Cyber Security

OS Detection: How Hackers Find Out What You Use

G5 Cyber Security

TL;DR

Hackers can often detect your operating system (Windows, macOS, Linux, etc.) through various techniques. This information helps them target you with specific attacks. However, there are steps you can take to make it harder for them.

How Hackers Detect Your OS

  1. TCP/IP Stack Fingerprinting: Every operating system sends slightly different data packets when communicating over the internet. Hackers analyse these ‘fingerprints’ to identify your OS.
    • Tools like Nmap can be used for this purpose (though it’s also a security tool!).
  2. User-Agent String: Your web browser sends a ‘User-Agent’ string to websites, which includes information about your OS and browser.
  3. HTTP Headers: Similar to the User-Agent, other HTTP headers can reveal OS details.
  4. JavaScript: JavaScript code running in your browser can detect OS information.
    • Hackers can inject malicious JavaScript into websites or use cross-site scripting (XSS) attacks.
  5. File Signatures & System Calls: If malware gets onto your system, it can directly identify the OS through file signatures and unique system calls.

How to Make OS Detection Harder

  1. Keep Your Software Updated: Updates often include security patches that address vulnerabilities used for OS detection and exploitation.
    • Enable automatic updates whenever possible.
  2. Use a Firewall: A firewall blocks unwanted network connections, making it harder for hackers to scan your system.
    • Windows Firewall is built-in; consider third-party options for more control.
  3. Privacy-Focused Browser Extensions: Some browser extensions can modify or block the User-Agent string and other identifying information.
    • Examples include Privacy Badger, uBlock Origin (which also blocks tracking scripts).
  4. Virtual Machines (VMs): Use a VM for risky activities. If the VM is compromised, your main OS remains safe.
    • Popular options: VirtualBox, VMware Workstation Player.
  5. VPN (Virtual Private Network): A VPN hides your IP address and encrypts your internet traffic, making it harder to track you.
  6. Disable JavaScript (Carefully): Disabling JavaScript can prevent some OS detection methods, but it will break many websites. Use with caution!
    • Browser settings usually allow disabling JavaScript globally or per-site.
  7. Regular Security Scans: Run regular scans with antivirus and anti-malware software to detect and remove any malicious code that might be identifying your OS.

Checking Your System Information (For Reference)

Knowing your system information can help you understand what hackers might see.

  1. Windows: Press Win+R, type msinfo32 and press Enter.
  2. macOS: Click the Apple menu > About This Mac.
  3. Linux: Open a terminal and use commands like 
    uname -a

    or 

    cat /etc/os-release

    .

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