A subtechnique of Anonymous Networking that routes traffic through a VPN server before entering the Tor network, creating a layered encryption scheme that complicates traffic analysis and hampers law enforcement efforts. Tor’s virtual tunnel system prevents websites and intermediaries from tracking online movements, and when combined with a VPN’s encrypted channel, adversaries obscure both the origin and destination of illicit funds. This multi-layered approach degrades attribution by forcing investigators to navigate multiple routing points and encrypted paths, making it significantly harder for AML compliance teams to monitor and trace transactions.
Onion over VPN
DEX
Peer-To-Peer Exchange
Trustless Exchange
Tactics
Onion over VPN employs a multi-layer encryption and routing approach that explicitly frustrates law enforcement or AML teams' ability to trace illicit fund flows by concealing both the origin and destination. This heightened anonymity and multiple routing points enhance operational secrecy, making it significantly harder to investigate or attribute transactions.
Risks
Onion over VPN exploits layered anonymizing channels by routing transactions through both a VPN and the Tor network. This multi-layer encryption and routing structure conceals IP addresses and real-world locations, undermining financial institutions’ ability to conduct effective transaction monitoring or trace illicit funds. By obscuring both origin and destination, criminals evade risk-based or geolocation checks and frustrate AML compliance efforts.
Indicators
Repeated user accesses or transactions initiated from IP addresses recognized as Tor exit nodes or known VPN servers.
User’s declared location (based on KYC records) consistently mismatched with frequent logins from diverse or rotating global IP addresses associated with VPN or Tor networks.
Multiple attempts to authenticate or transact using IP addresses flagged for Tor/VPN usage, followed by immediate successful connections from alternate anonymizing services.
Data Sources
- Records login attempts, authentication failures, and suspicious device/browser fingerprints.
- Highlights anomalies in user session patterns (e.g., sudden IP address changes, usage of known anonymizing IPs).
- Assists in correlating frequent or failed logins through Tor/VPN networks with potential illicit activity masked by multi-layered encryption.
- Captures IP addresses, authentication events, and timestamps for user logins and web traffic.
- Allows detection of repeated access attempts from Tor exit nodes or known VPN servers.
- Enables investigators to correlate anomalous login locations with potential use of anonymous networking techniques, supporting timely identification of Onion over VPN usage.
- Contains customer identity and declared location details, correlating official user information with observed system access.
- Facilitates discrepancy analysis between stated residency and the IP geolocation from which transactions/logins originate.
- Supports detecting location mismatches indicative of Onion over VPN usage, aiding AML investigations.
Mitigations
Apply deeper verification steps for customers consistently accessing services via Tor or VPN. Require documented justifications for anonymized connections, verify the source of funds, and scrutinize transaction behaviors to spot discrepancies with declared user profiles. This closes gaps that onion over VPN usage could exploit.
Implement specialized detection rules for repeated usage of known Tor exit nodes or VPN servers, correlating abrupt IP changes and large or rapid-fire transactions with location obfuscation. By focusing on these anomalies, institutions can promptly flag potential layering attempts masked by onion over VPN.
Enforce strong authentication, such as multi-factor authentication or biometrics, combined with continuous IP monitoring to flag repeated usage of anonymizing networks. Users connecting from Tor or VPN endpoints should trigger an immediate challenge-response or step-up verification to ensure genuine account control despite IP masking.
Restrict or require immediate additional checks for logins from recognized Tor exit nodes or VPN addresses. Impose enhanced measures, such as real-time re-authentication or temporary transaction caps, on users who frequently use anonymous networks until they validate a legitimate business case for such usage.
Instruments
- Onion over VPN adds an additional layer of anonymity on top of privacy coins’ built-in obfuscation features, such as stealth addresses and ring signatures. Investigators must overcome not only blockchain-level privacy but also multiple network encryption layers.
- This multi-tier approach significantly hinders any attempt to match transaction flows or wallet addresses with real-world identities, further reducing the traceability of illicit proceeds.
- By accessing wallets through an Onion over VPN connection, criminals obscure the IP addresses used to log in or sign blockchain transactions. This thwarts platforms and investigators that rely on network metadata to identify suspicious account usage.
- Such layering of anonymizing services also inhibits link analysis tying multiple wallet activities back to a common user, thereby complicating AML compliance and investigative efforts.
- Criminals exploit Onion over VPN to trade stablecoins on peer-to-peer or decentralized platforms, bypassing conventional IP-based monitoring or geolocation restrictions.
- Because stablecoins maintain a consistent fiat-pegged value, layering such transactions behind multiple encryption points makes it even harder for AML teams to detect suspicious fund flows, as movements appear routine and geographically unlinked.
- Criminals route transactions over Onion over VPN to hide their originating IP addresses when sending or receiving public ledger cryptocurrencies (e.g., Bitcoin or Ethereum). This technique frustrates investigators who rely on IP geolocation or node-level data to connect specific wallet addresses to real individuals.
- By masking the true source of transactions, criminals can execute payments or move funds without revealing identifiable network attributes, complicating attribution and traceability efforts.
Service & Products
- DeFi protocols lack a centralized intermediary, allowing criminals to exploit Tor+VPN to evade IP-based controls.
- The multi-layered anonymity channel significantly undermines investigative efforts, masking fund flows through smart contracts.
- Users connect directly for crypto trades, and combining Tor with a VPN obscures both parties' locations and IP addresses.
- This anonymity fosters untraceable transfers, as participants can sidestep stricter AML controls through decentralized interactions.
- Enables near-instant cross-chain asset conversions while hiding under layered encryption, leaving minimal transactional footprints.
- By routing connections through Tor and VPN, criminals circumvent location and risk-based checks typically used to flag suspicious exchange activities.
- Criminals can register and operate exchange accounts through multiple encrypted layers, preventing IP-based or geolocation checks.
- The usage of Onion over VPN hinders law enforcement’s ability to trace and link transactions to real-world identities, facilitating the layering of illicit proceeds.
Actors
Professional money launderers use Onion over VPN connections to:
- Obscure their real-world identities when accessing virtual asset exchanges or peer-to-peer trading platforms.
- Thwart IP-based monitoring and geolocation checks, making it harder for financial institutions to detect or link suspicious transactions.
This multi-layered anonymity channel facilitates the seamless layering of illicit funds, diminishing the effectiveness of AML teams' traceability efforts.
Virtual asset service providers are exploited when criminals route their connections through Onion over VPN to:
- Conceal user location and IP data, bypassing risk-based or geolocation-based transaction monitoring.
- Open or operate accounts without revealing accurate network identifiers, hindering robust KYC and investigative processes.
This exploitation significantly impedes the provider’s ability to flag unusual activity and collaborate with financial institutions on suspicious transaction investigations.
References
FinCEN (Financial Crimes Enforcement Network). (2021). Financial trend analysis: Ransomware trends in Bank Secrecy Act data between January 2021 and June 2021. FinCEN. https://www.fincen.gov/resources/advisoriesbulletinsfact-sheets
Irwin A. S.M., Slay J., Choo K.R., Liu L. (2013). Are the financial transactions conducted inside virtual environments truly anonymous? An experimental research from an Australian perspective. Journal of Money Laundering Control, Vol. 16 No. 1, pp. 6-40. https://doi.org/10.1108/13685201311286832