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Hello Hacker's in this Blog, We have to show and Setup WhatsApp or Signal Tracker Using RTT(Round-Trip-Time), so Let's Start.

🔎 Introduction

Instant messaging apps like WhatsApp and Signal prioritize end-to-end encryption, but they may still leak subtle data about a user’s device behavior. The Device Activity Tracker project is an open-source proof-of-concept (PoC) that demonstrates how the timing of delivery receipts—specifically the round-trip time (RTT)—can be used to infer whether a target device is actively used, idle, or offline, using only the phone number.

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This leverages research outlined in the academic paper “Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers,” which shows this kind of fingerprinting can reveal sensitive patterns such as active usage, standby mode, and network changes.

🧠 How It Works

At a high level:

The tracker sends specially crafted probe messages via WhatsApp or Signal.

It measures how long it takes (RTT) for those messages to be acknowledged by the recipient device.

Because RTT can vary depending on device state (active vs idle vs offline), statistical patterns can be inferred.

Lower RTT usually indicates active use, while higher RTT suggests standby or offline state.

The tool supports both a web interface (React frontend + Node.js backend) and a CLI interface for basic RTT tracking.

🛠️ Installation & Setup Guide

This section walks you through setting up Device Activity Tracker from scratch on Ubuntu / Debian-based systems.

✅ System Requirements

Before starting, make sure you have:

Ubuntu 20.04 / 22.04 / 24.04 (recommended)

Internet connection

A WhatsApp account for QR authentication

Root or sudo access

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🔹 Node.js 20.x Installation

The project requires Node.js 20.x or higher. Use the official NodeSource installer:

curl -fsSL https://deb.nodesource.com/setup_20.x | sudo -E bash - 

sudo apt install -y nodejs

🔹 Docker Installation (Required)

Docker is mandatory for running the Signal API and related services.

Step 1: Update system and install dependencies

sudo apt install -y ca-certificates curl gnupg lsb-release

Step 2: Add Docker’s official GPG key

sudo mkdir -p /etc/apt/keyrings curl -fsSL https://download.docker.com/linux/ubuntu/gpg | \ sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

Step 3: Add Docker repository

echo \ "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] \ https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) stable" | \ sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

Step 4: Install Docker Engine & tools

sudo apt update 

sudo apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 5: Start & enable Docker

sudo systemctl start docker 

sudo systemctl enable docker

🔹 Clone the Project

git clone https://github.com/gommzystudio/device-activity-tracker.git 

cd device-activity-tracker

🔹 Install Project Dependencies

npm install 

cd client && npm install && cd ..

🔧 Required IP Configuration (Important)

After npm install, replace localhost with your IPv4 address to avoid connection issues.

Edit client/src/app.tsx (line 7) and change the WebSocket URL to ws://YOUR_IPV4:3001.

Then edit src/server.ts (line 21) and bind the server to 0.0.0.0 instead of localhost.

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🔹 Start the Application

Start backend (Signal API + WebSocket server)

npm run start:server

Start frontend (React UI)

npm run start:client

🌐 Access the Web Interface

http://yourip:3000

Visit http://yourip:3000 in your browser.

Scan the QR code with your WhatsApp account to authenticate.

Enter a target phone number (e.g., +491701234567).

📊 Reading the Output

Online: RTT below threshold → device in active use.

Standby: RTT above threshold → device is idle/locked.

Offline: No ACK received → unreachable

🧩 Security & Ethical Concerns

This project vividly demonstrates that encrypted messaging apps are not fully privacy-opaque. Even without reading message content, delivery mechanisms and timing leaks can reveal user behavior. Recent security reporting confirms such tools can be used to infer when a person is active, offline, at home, or asleep.

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⚙️ Why This Matters

Even high-security apps like WhatsApp and Signal are susceptible to subtle privacy leaks:

✅ Shows how delivery receipts and networking timing produce unintended channels of information

✅ Raises awareness about the lesser-known risks of messaging app traffic

✅ Offers a hands-on reference for researchers, auditors, and cybersecurity students to explore messaging protocol side-channels

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