Tornado Cash Hack

TOTAL LOST $1.0M
Medium Other

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain 2023 Incident surface
Recovered - No recovery reported
All-Time Rank #825 By amount stolen
Auditors 1 Prior security audit

Incident Overview

Quick Summary

Tornado Cash Governance was exploited through a malicious proposal, and the attacker gained control of the governance.

Details of the Exploit

Tornado Cash is a service that provides non-custodial anonymous transactions on EVM chains. The project's Governance was exploited via malicious proposal. On May 20th, 2023 Tornado Cash governance ceased to exist as an attacker granted themselves over 1.2 million fake votes through a malicious proposal.

With full control of governance, they could withdraw all locked votes and drain tokens from the contract or brick the router. The attack was sophisticatedly designed by using various tricks like combining CREATE/CREATE2 to create a contract with different bytecode and hiding intent behind emergencyStop() named function while updating proposal logic to grant themselves fake votes. Once gaining control, the attacker drained various contracts and users staking assets as $TRON tokens.

The stolen tokens were swapped for $ETH and 360 $ETH was transferred through TornadoCash, while 120.4 $ETH remains at the attacker's address along with 177,340 $USD worth $TORN tokens. Consequently, over 500,000 $TORN tokens were used by the attacker to propose the 21st proposal, which seemingly may return the protocol control back to the users. The total stolen amount reached 1,049,513 $USD, and maybe even more cause of locked $TORN tokens in the next proposal from the attacker.

Block Data Reference

Attacker's Funds Holder Address:

https://etherscan.io/address/0x09212366…77bD59

Malicious Proposal Executor Address:

https://etherscan.io/address/0x59234095…789de9

Proposal Execution Transaction:

https://etherscan.io/tx/0x3274b609…75486d

Selfdestruct Transaction:

https://etherscan.io/tx/0xd3a570af…391adb

Vote Gain Transaction:

https://etherscan.io/tx/0xa7d20ccd…620122

Malicious Proposal:

https://etherscan.io/address/0xC503893b…52752D

21st Proposal:

https://etherscan.io/address/0x1FAd009a…E31e23#code

Incident Report

Protocol / Project Tornado Cash
Date of Incident
Attack Technique Other
Classification Other
Primary Source View Post-Mortem #1 View Post-Mortem #2

Protocol Information

Protocol Type Privacy
Affected Token TORN
Official Website tornado.ws/
Protocol Twitter/X @TornadoCash
Team Public / Doxxed
Source Code Verified On-Chain

Market Context at Time of Hack

Token Categories
Privacy DAO Ethereum Ecosystem BNB Chain Ecosystem Optimism Ecosystem Privacy Coins
Protocol Links
GitHub

What the Attacker Needed to Succeed

Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.

Technical Knowledge Deep understanding of other and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in Tornado Cash's contract logic - root cause: other
Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block
Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Other audit checklist and test coverage
Audited by Pessimistic — still lost $1.0M. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Tornado Cash, these are the critical security checks that could have prevented this incident (May 2023).

  • Verify all logic paths related to Other are guarded by proper access controls and input validation
  • Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

Free Trial

Security Audit History

Sources & References

Browse all hacks

These hacks used the same attack technique. Understanding the pattern helps prevent future exploits.

DeFiTuna $570K
Other
Cascade $1.3M
Other
Lumi Finance $264K
Other
Hinkal $820K
Other
AIDCToken $121K
Other
Polymarket $3.0M
Other

Learn to Prevent the Next Tornado Cash

The Tornado Cash hack is one of many attacks that skilled auditors are trained to detect before deployment. Master real exploit patterns and defense techniques with hands-on Web3 security training.

Start Free Trial Browse Attack Library
Recreate exploit patterns safely Free Trial