VPN leaks occur when a user's real IP address or DNS queries are accidentally exposed while connected to a VPN. Here are common leak types and protection methods:
Common Leak Types
1. DNS Leaks
Causes:
- Operating system bypasses VPN DNS settings
- VPN client not properly configured for DNS
- Using ISP default DNS servers
Detection Methods:
- Visit dnsleaktest.com or ipleak.net
- Compare DNS servers before and after enabling VPN
Protection Measures:
- Force use of VPN-provided DNS servers
- Disable operating system DNS caching
- Use DNS over HTTPS (DoH) or DNS over TLS (DoT)
- Block non-VPN DNS queries in firewall rules
2. IPv6 Leaks
Causes:
- VPN only handles IPv4 traffic, IPv6 traffic goes directly through ISP
- Operating system prefers IPv6
Detection Methods:
- Visit test-ipv6.com
- Check if IPv6 address is displayed
Protection Measures:
- Disable IPv6 in VPN client
- Disable IPv6 at operating system level
- Use VPN protocols that support IPv6 (like WireGuard)
3. WebRTC Leaks
Causes:
- WebRTC API can bypass VPN to get real IP
- Browser establishes direct P2P connections
Detection Methods:
- Visit browserleaks.com/webrtc
- Check displayed IP addresses
Protection Measures:
- Disable WebRTC in browser settings
- Use browser extensions (like uBlock Origin) to block WebRTC
- Use browsers that don't support WebRTC (like Tor Browser)
4. Kill Switch Failures
Causes:
- VPN connection unexpectedly drops
- Kill Switch not properly configured or fails
- Applications continue using network after VPN disconnects
Protection Measures:
- Enable and test Kill Switch functionality
- Use firewall rules to block non-VPN traffic
- Choose reliable VPN service providers
5. Application Leaks
Causes:
- Certain applications bypass VPN (like BitTorrent)
- System services use independent network connections
Protection Measures:
- Use Split Tunneling configuration
- Force specific applications to use VPN in firewall
- Monitor all network connections
6. Time Leaks
Causes:
- System time inconsistent with VPN server timezone
- Some websites infer location from timezone
Protection Measures:
- Synchronize system time
- Use VPN server's timezone
7. Super Cookies
Causes:
- Flash Cookies or LocalStorage leaking location information
- Browser fingerprinting
Protection Measures:
- Regularly clear browser data
- Use private browsing mode
- Use anti-fingerprinting browser extensions
Comprehensive Protection Strategy
1. Choose Reliable VPN Service
- No-logs policy
- Independently audited
- Provides leak protection features
- Supports multiple protocols
2. Properly Configure VPN Client
- Enable all leak protection options
- Use VPN-provided DNS
- Enable Kill Switch
- Regularly update client
3. System-level Protection
- Disable IPv6 (if not needed)
- Configure firewall rules
- Regularly check network connections
- Use privacy protection tools
4. Browser Protection
- Disable WebRTC
- Use private browsing mode
- Install privacy protection extensions
- Regularly clear cookies
5. Regular Testing
- Use multiple leak detection websites
- Test different applications
- Check log files
- Monitor network traffic
Recommended Detection Tools
- Comprehensive Detection: ipleak.net, dnsleaktest.com
- WebRTC Detection: browserleaks.com/webrtc
- IPv6 Detection: test-ipv6.com
- DNS Detection: dnsleak.com
- Comprehensive Privacy Detection: privacy.net/analyzer
Best Practices
- Perform leak testing before using VPN
- Regularly check and update VPN configuration
- Use multiple detection tools for cross-verification
- Stay informed about VPN service provider security announcements
- Understand leak risks of different protocols
- Keep system and applications updated
- Use multi-layer protection strategies