What is Cover Traffic?
Dummy data transmitted alongside real communications to prevent traffic analysis from revealing when you're actually communicating.
Cover traffic defeats surveillance that watches for patterns in when and how much you communicate.
The Problem
- Even with encrypted communications, an observer can see WHEN you send messages
- Traffic patterns reveal relationships (Alice always messages Bob at 9pm)
- Sudden spikes in encrypted traffic correlate with real events
- Silence is also a signal (no traffic after an event = you might have been involved)
How Cover Traffic Works
- Constant stream of data is transmitted regardless of real activity
- Real messages are hidden within the noise
- Traffic volume and timing remain consistent
Implementations
- Tor: Sends fixed-size cells to prevent size-based analysis
- Some VPNs: Offer padding to obscure traffic patterns
- Briar: Generates cover traffic when connected to contacts
Trade-offs
Cover traffic increases bandwidth usage and power consumption. Most people don't need it — it's primarily relevant for high-risk individuals under active surveillance.
Related Terms
Metadata
Data about data. In the context of communications, metadata includes information like who you contacted, when, for how long, and from where—everything except the actual content of your message. Metadata can reveal intimate details about your life even when content is encrypted.
Operational Security
The practice of protecting sensitive information by thinking like an adversary to identify vulnerabilities in your own behavior and communications. OPSEC goes beyond technical tools to address human factors that could expose you.
Traffic Analysis
The process of examining patterns in communication metadata—who talks to whom, when, how often, and how much—to extract intelligence without accessing content. Even encrypted communications leak metadata that can reveal sensitive information.
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