Coincheck Hack

TOTAL LOST $534M
Critical #24 All-Time Private Key Compromised (Unknown Method) / Other nem

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain nem Incident surface
Recovered $534.0M 100.0% returned
All-Time Rank #24 By amount stolen
Protocol Type Exploit/Other Target category

Incident Overview

Quick Summary

On Jan. 26, about 523 million NEM (XEM) tokens, valued at over $530 million at the time, were illicitly transferred from its hot wallet address, resulting in an anomalous drop in the Japanese exchange's balance.

Details of the Exploit

The attack was made possible by the company's technological issues and staff scarcity, which resulted in inadequate security measures. The stolen NEM were held on an internet-connected hot wallet rather than an offline cold wallet.

Coincheck utilized its own funds to compensate all 260,000 impacted clients:

https://www.ft.com/content/6a761a60-2694-11e8-b27e-cc62a39d57a0

Block Data Reference

Attacker address:

https://explorer.nemtool.com/#/s_account?account=NC4C6PSUW5CLTDT5SXAGJDQJGZNESKFK5MCN77OG

Malicious transaction example:

https://explorer.nemtool.com/#/s_tx?hash=c2921d538a6192bf35e0bb49cefcf6aa8e19acb3fef08f70f5b6b977d9d50aee

This is classified as a Access Control Attacks . Compare similar hacks →

Incident Report

Protocol / Project Coincheck
Date of Incident
Affected Chain(s) nem
Attack Technique Private Key Compromised (Unknown Method) / Other
Classification Infrastructure / CeFi
Primary Source View Post-Mortem

Protocol Information

Protocol Type Exploit/Other
Official Website coincheck.com/
Protocol Twitter/X @coincheckjp
Team Anonymous
Source Code Unverified

Market Context at Time of Hack

Token Categories
Education Polygon Ecosystem
Protocol Links
Discord

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 Operational-security tradecraft (phishing, malware, leaked seed phrases, or insider access) to obtain treasury signing authority
Capital Required Minimal capital - only enough to cover gas while draining the compromised accounts
On-Chain Access Valid signing authority over the compromised wallets / multisig signers, allowing direct transfer of funds or stake authorization
Target Reconnaissance Identification of Coincheck's high-value treasury accounts and the authority / multisig structure controlling them
Execution Speed Speed to drain the compromised accounts before the team detects the breach and revokes signing authority or freezes the assets
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? Hard to catch — private key / OpSec failures are outside smart contract audit scope

If you're auditing a protocol with similar architecture to Coincheck, these are the critical security checks that could have prevented this incident (January 2018).

  • Verify all logic paths related to Private Key Compromised (Unknown Method) / Other are guarded by proper access controls and input validation - see the Access Control Attacks attack class for patterns
  • 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.

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Funds Recovery

100.0%

Recovered

$534.0M

Net Loss

0

Related Attack Classes

The technique used in this hack maps to these vulnerability classes in our security curriculum:

See all Access Control Attacks examples →

Access Control Attacks

Sources & References

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

Phemex $85.0M
Private Key Compromised (Unknown Method) / Other
Stake.com $41.4M
Private Key Compromised (Unknown Method) / Other
DAO Maker Vesting $7.0M
Private Key Compromised (Unknown Method) / Other

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