OpenVPN is Open to VPN Fingerprinting

Diwen Xue, Reethika Ramesh, Arham Jain, Michalis Kallitsis, J. Alex Halderman, Jedidiah R. Crandall, Roya Ensafi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

VPN adoption has seen steady growth over the past decade due to increased public awareness of privacy and surveillance threats. In response, certain governments are attempting to restrict VPN access by identifying connections using “dual use” DPI technology. To investigate the potential for VPN blocking, we develop mechanisms for accurately fingerprinting connections using OpenVPN, the most popular protocol for commercial VPN services. We identify three fingerprints based on protocol features such as byte pattern, packet size, and server response. Playing the role of an attacker who controls the network, we design a two-phase framework that performs passive fingerprinting and active probing in sequence. We evaluate our framework in partnership with a million-user ISP and find that we identify over 85% of OpenVPN flows with only negligible false positives, suggesting that OpenVPN-based services can be effectively blocked with little collateral damage. Although some commercial VPNs implement countermeasures to avoid detection, our framework successfully identified connections to 34 out of 41 “obfuscated” VPN configurations. We discuss the implications of the VPN fingerprintability for different threat models and propose short-term defenses. In the longer term, we urge commercial VPN providers to be more transparent about their obfuscation approaches and to adopt more principled detection countermeasures, such as those developed in censorship circumvention research.

Original languageEnglish (US)
Title of host publicationProceedings of the 31st USENIX Security Symposium, Security 2022
PublisherUSENIX Association
Pages483-500
Number of pages18
ISBN (Electronic)9781939133311
StatePublished - 2022
Event31st USENIX Security Symposium, Security 2022 - Boston, United States
Duration: Aug 10 2022Aug 12 2022

Publication series

NameProceedings of the 31st USENIX Security Symposium, Security 2022

Conference

Conference31st USENIX Security Symposium, Security 2022
Country/TerritoryUnited States
CityBoston
Period8/10/228/12/22

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Information Systems
  • Safety, Risk, Reliability and Quality

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