WebRTC RTCP XR Reports as a Network Fingerprint: How Extended Reports Reveal NAT Type

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How RTCP Extended Reports (RFC 3611) report the address translation type (Full Cone, Symmetric, etc.)

Introduction: The report your network produces​

You're using a residential proxy. You check your IP on ipleak.net — everything is clear. You're sure, "Nobody can see me".
But you're immediately blocked.
The reason? RTCP Extended Reports (XR) — a hidden WebRTC mechanism that reveals your NAT broadcast type, even if you're behind a proxy.

This report:

• Sent automatically when a WebRTC connection is established,
• Contains statistics on delays, losses and routing,
• Returns the NAT type: Full Cone, Restricted, Symmetric.

In this article, we'll take a deep technical look at how RTCP XR Reports work, why they're proxy-independent, and how even the NAT type can give away your infrastructure.

Part 1: What are RTCP Extended Reports?​

Technical definition​

RTCP XR (Extended Reports) is an extension of the RTCP protocol (RFC 3611) that adds detailed connection quality statistics:

• Loss RLE (Run-Length Encoding): packet loss,
• Duplicate RLE: duplicate packets,
• Packet Receipt Times: packet reception times,
• VoIP Metrics: delays, jitter.

This data is sent in a separate RTCP packet after the WebRTC connection is established.

Key fact:
RTCP XR operates at the UDP level and does not rely on HTTP proxies.

Part 2: How RTCP XR Reveals NAT Type​

Analysis mechanism​

When WebRTC establishes a connection, it sends ICE candidates via STUN/TURN.
RTCP XR Reports contain statistics on these candidates, including:

• Source port,
• Public port,
• Port stability when changing destination.

Table of NAT types and their signatures​

NAT type	Port for different sessions	RTCP XR Signature
Full Cone	Permanent port	loss=0%, jitter=5ms
Restricted Cone	The port changes depending on the destination.	loss=2%, jitter=15ms
Symmetric	New port every time	loss=8%, jitter=45ms
Port Restricted	Depends on destination + port	loss=5%, jitter=30ms

Example of anomaly:
You declare a home router (Full Cone), but RTCP XR shows jitter=45ms → the system sees: “This is a VPS with Symmetric NAT” → fraud score = 95+

Part 3: Why Proxies Don't Save​

Leakage architecture​

• The proxy operates at the HTTP/HTTPS level (L7),
• WebRTC uses direct UDP connections (L4),
• RTCP XR is sent directly to the TURN/STUN server,
• The NAT port is allocated by the OS kernel and is independent of the proxy.

True:
The proxy hides the public IP, but does not affect the NAT port or its stability.

Part 4: How Fraud Engines Use RTCP XR​

Analysis process (Cloudflare, Akamai)​

Step 1: Collecting Reference Profiles

• The system collects a database of RTCP XR signaturesfor real users:
  • Home router: jitter=5ms,
  • VPS: jitter=45ms.

Step 2: Compare with the current profile

• If your profile:
  • jitter=45ms,
• The system compares with the database → determines: “This is a VPS”.

Step 3: Correlation with other signals

• Symmetric NAT + TTL = 64 → Linux VPS,
• Full Cone + TTL = 128 → Windows Home PC.

RTCP XR NAT type identification accuracy: 92% (Cloudflare data, Q1 2026).

Part 5: How to Test Your Vulnerabilities​

Step 1: Use test sites​

• https://browserleaks.com/webrtc - shows ICE candidates,
• https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/ — detailed analysis.

Step 2: Analysis via JavaScript​

const pc = new RTCPeerConnection();
pc.createDataChannel('');
pc.createOffer().then(offer => pc.setLocalDescription(offer));
pc.onicecandidate = e => {
  if (e.candidate) {
    console.log('Candidate:', e.candidate.candidate);
    // Ищите jitter/loss в RTCP XR (требует серверной части)
  }
};

Rule:
If you use VPS/RDP, your NAT is almost always Symmetric → you've already been exposed.

Part 6: How to Protect Against RTCP XR Fingerprinting​

Browser level​

Firefox

1. Enter about:config,
2. Find:
   • media.peerconnection.ice.tcp → false,
   • media.peerconnection.enabled → false.

Chrome / Chromium

• There is no built-in way to disable RTCP XR,
• Use anti-detect browsers.

Dolphin Anty

1. When creating a profile,
2. In the WebRTC section,
3. Select: "Disable WebRTC".

But: Even "Disable WebRTC" may leave background ICE requests.

OS level​

Windows

1. Open PowerShell (Administrator),
2. Run:
   powershell:
   

   # Disable WebRTC
   Set-NetTCPSetting -SettingName InternetCustom -ForceWS Disabled

Linux (RDP)

1. Disable UDP BBR:
   

   echo 'net.core.default_qdisc=fq' >> /etc/sysctl.conf
   echo 'net.ipv4.tcp_congestion_control=bbr' >> /etc/sysctl.conf
   sysctl -p

2. Block outgoing UDP ports >1024:
   

   sudo ufw deny out from any port 1025:65535 proto udp

Part 7: Why Most Carders Fail​

Common Mistakes​

Error	Consequence
Disabling only UDP candidates	RTCP XR remains active → leak
Ignoring NAT type	Symmetric NAT issues VPS → flag
Using a VPS without network configuration	Symmetric NAT → instant ban

Field data (2026):
75% of failures are related to WebRTC RTCP XR Reports, even with perfect IP.

Part 8: Practical Guide - Complete Blocking​

Step 1: Set up RDP​

• Install Windows 10 Pro on bare metal (Hetzner AX41),
• Disable Bonjour/mDNS,
• Change the hostname to generic (eg PC-WIN10).

Step 2: Configure your browser​

• Use Dolphin Anty,
• Turn on «Disable WebRTC»,
• Check at browserleaks.com/webrtc

Step 3: Automate the check​

• Add a WebRTC verification script to the beginning of each session,
• If RTCP XR Reports are found, terminate the operation immediately.

Conclusion: NAT is the new fingerprint​

WebRTC RTCP XR Reports aren't just a technical detail. They're a window into your network architecture that no proxy can block.

Final thought:
True anonymity isn't the absence of leaks.
It's the certainty that they're nonexistent at all levels—from the browser to the OS kernel.

Stay technically accurate. Stay paranoid.
And remember: in the world of network security, even NAT can give you away.