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Mt. Gox

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Summary

Mt. Gox was a Tokyo-based Bitcoin exchange that, at its peak in 2013–2014, handled approximately 70% of all global Bitcoin transactions. In February 2014 it suspended trading and filed for bankruptcy after disclosing the loss of approximately 850,000 BTC — later revised to approximately 650,000 BTC net — due to theft that investigators determined began as early as late 2011. Creditor repayment proceedings under civil rehabilitation law have been ongoing since 2018, with partial distributions commencing in July 2024 and a current deadline of October 31, 2026.

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Background and Founding

The domain mtgox.com was registered in January 2007 by American programmer Jed McCaleb, originally intended as a trading platform for Magic: The Gathering Online cards — the name is an acronym for 'Magic: The Gathering Online eXchange.' McCaleb repurposed the site as a Bitcoin exchange in July 2010, following a Slashdot article about Bitcoin. In March 2011, McCaleb sold Mt. Gox to French developer Mark Karpeles, who was residing in Japan. Under Karpeles, Mt. Gox grew rapidly to become the world's dominant Bitcoin exchange, at its height processing more than 70% of all global Bitcoin trades.

Sources

June 2011 Security Incident

In June 2011, Mt. Gox suffered its first publicly known security breach. On June 19, 2011, a hacker used credentials reportedly obtained from a compromised Mt. Gox auditor's computer to access the exchange's administrative system, artificially driving the nominal Bitcoin price on the exchange to one cent and transferring an estimated 2,000 BTC from customer accounts. The incident affected accounts with balances totaling more than $8.75 million at prevailing prices. Mt. Gox suspended trading briefly and later reimbursed affected users. Separately, investigators later concluded that the more consequential theft — the compromise of Mt. Gox's hot wallet private keys — began around September 2011, distinct from the June incident.

Sources

The Primary Theft: 2011–2014 Hot Wallet Compromise

Independent security researcher Kim Nilsson of Tokyo-based firm WizSec published findings in April 2015 concluding that most or all of the missing Mt. Gox bitcoins were stolen from the exchange's hot wallet over an extended period beginning in late 2011. According to WizSec, the Mt. Gox hot wallet's private keys (a wallet.dat file) were copied and stolen around September 2011, giving the attacker ongoing access to any Bitcoin deposited to addresses whose keys were in that file. By mid-2013, the attacker had drained approximately 630,000 BTC. WizSec's blockchain analysis linked the stolen funds to wallets controlled by Alexander Vinnik, who later moved substantial amounts to the BTC-e exchange. Approximately 300,000 BTC were traced to BTC-e. Mt. Gox's management has alleged it was unaware of the systematic draining for years. In February 2014, when internal audits and customer withdrawal problems forced a public disclosure, approximately 850,000 BTC was reported missing — 750,000 belonging to customers and approximately 100,000 belonging to the company itself. On March 20, 2014, Mt. Gox reported recovering 199,999.99 BTC from an old wallet predating June 2011, reducing the net loss to approximately 650,000 BTC.

Sources

Transaction Malleability Claim

In February 2014, Mt. Gox publicly attributed a portion of its losses to a Bitcoin protocol vulnerability known as transaction malleability, in which an attacker could alter a transaction's ID before confirmation, potentially causing the sender to re-broadcast the same payment and thus pay twice. A subsequent peer-reviewed study published by researchers at ETH Zurich and the Swiss Federal Institute of Technology estimated that, at most, fewer than 400 BTC could realistically have been stolen from Mt. Gox via this specific mechanism — far short of the hundreds of thousands reported missing. MIT Technology Review and other outlets noted significant holes in Mt. Gox's public account. WizSec's later analysis pointed to the private key compromise as the actual cause of the overwhelming majority of losses, making the transaction malleability explanation widely regarded as incomplete or misleading.

Sources

Collapse and Bankruptcy Filing

On February 7, 2014, Mt. Gox halted all Bitcoin withdrawals, citing transaction malleability issues. On February 25, 2014, the exchange suspended all trading and its website went offline. On February 28, 2014, Mt. Gox filed in the Tokyo District Court for a form of creditor protection known as minji saisei (civil rehabilitation), disclosing the loss of approximately 850,000 BTC worth approximately $473 million at the time of filing. The collapse caused Bitcoin's price to fall approximately 36% over February and March 2014. On April 24, 2014, the Tokyo District Court approved conversion of the proceedings to bankruptcy liquidation. From February 2014 through the end of March 2014, Bitcoin's market price declined approximately 36%.

Sources

Mark Karpeles: Arrest, Trial, and Verdict

Mark Karpeles, the CEO and majority owner of Mt. Gox, was arrested by Japanese authorities on August 1, 2015 on suspicion of accessing the Mt. Gox computer system to manipulate account balances. He spent more than 11 months in pre-trial detention. Tokyo prosecutors indicted Karpeles on charges of embezzlement and aggravated breach of trust, seeking a 10-year prison sentence. Karpeles pleaded not guilty to all charges. On March 14, 2019, the Tokyo District Court acquitted Karpeles of embezzlement and breach of trust, but found him guilty of one count of data manipulation for falsifying electronic records to inflate Mt. Gox's apparent holdings by approximately $33.5 million. He was sentenced to 30 months imprisonment, suspended for four years, meaning he served no additional jail time provided he committed no further offenses within that period. On June 12, 2020, Tokyo's High Court upheld the original verdict and suspended sentence on appeal. Karpeles was never charged with direct theft of the 650,000 BTC, as prosecutors were unable to establish criminal liability for the hack itself.

Sources

DOJ Indictment of Russian Nationals

In June 2023, the United States Department of Justice unsealed an indictment charging Russian nationals Alexey Bilyuchenko and Aleksandr Verner with conspiring to launder approximately 647,000 BTC stolen from Mt. Gox. According to the indictment, the two gained unauthorized access to Mt. Gox wallets around September 2011 and stole cryptocurrency over a period extending through at least May 2014. The stolen funds were allegedly laundered through an unnamed New York-based Bitcoin brokerage service and through the BTC-e exchange, which the DOJ alleged Bilyuchenko helped operate. Bilyuchenko was also charged with operating an unlicensed money services business in connection with BTC-e. Separately, Alexander Vinnik — alleged operator of BTC-e — was previously charged and later extradited to the United States on related money laundering charges. The indictment corroborated WizSec's earlier independent blockchain analysis linking the Mt. Gox theft to the BTC-e ecosystem.

Sources

Civil Rehabilitation and Creditor Repayment

In June 2018, following a request by creditors, the Tokyo District Court converted Mt. Gox's liquidation proceedings back to civil rehabilitation, appointing Nobuaki Kobayashi as rehabilitation trustee. The civil rehabilitation process allowed creditors to receive repayment in Bitcoin rather than in yen at 2014 valuations, which was advantageous given Bitcoin's subsequent appreciation. The rehabilitation plan was approved by creditors and sanctioned by the Tokyo court. Repayment distributions began in July 2024 — more than a decade after the collapse — with Bitcoin and Bitcoin Cash distributed to creditors through designated exchange platforms including Kraken, Bitstamp, and BitGo. By August 2024, over 21,000 creditors had received distributions. On October 10, 2024, trustee Kobayashi announced that most repayments to verified creditors had been completed. Additional repayments were made from January through March 2025, bringing the total number of creditors paid to over 19,500. Because Bitcoin's price had risen from approximately $450 (2014 valuations) to well above $50,000, creditors who had completed required verification procedures received substantially more in dollar terms than their original losses. The repayment deadline has been extended three times: from 2023 to October 2024, then to October 2025, and most recently to October 31, 2026, citing creditors who had not completed required procedural steps. As of late 2025, approximately 34,000 BTC valued at more than $4 billion remained in Mt. Gox estate wallets awaiting distribution to outstanding creditors.

Sources

Regulatory Impact

The collapse of Mt. Gox prompted Japan to establish the first formal regulatory framework for cryptocurrency exchanges and virtual currencies. Japan enacted the Virtual Currency Act in 2016 (part of the amended Payment Services Act), requiring exchanges to register with the Financial Services Agency, maintain segregated customer funds, and implement security standards. The episode is widely cited in regulatory and academic literature as a foundational case study in custodial exchange risk and the dangers of operating without adequate security audits, internal controls, or reserve transparency.

Sources

Timeline

2007-01-01

Jed McCaleb registers mtgox.com as a Magic: The Gathering Online card trading platform.

Mt. Gox — Wikipedia

2010-07-01

McCaleb relaunches mtgox.com as a Bitcoin exchange after reading about Bitcoin on Slashdot.

What Is Mt. Gox? — Gemini Cryptopedia

2011-03-01

McCaleb sells Mt. Gox to Mark Karpeles for approximately $0 plus a share of future profits.

Mt. Gox — Wikipedia

2011-06-19

Hacker uses compromised auditor credentials to set Bitcoin price to $0.01 on Mt. Gox and steal approximately 2,000 BTC. Exchange suspends trading briefly.

The History of the Mt Gox Hack — Blockonomi

2011-09-01

Mt. Gox hot wallet private keys (wallet.dat file) are copied and stolen, per WizSec blockchain analysis. Systematic theft of incoming deposits begins.

WizSec: The Missing MtGox Bitcoins

2013-06-01

Approximately 630,000 BTC has been drained from the compromised hot wallet by mid-2013, per WizSec analysis.

WizSec: Breaking Open the MtGox Case, Part 1

2014-02-07

Mt. Gox halts all Bitcoin withdrawals, initially citing transaction malleability issues.

Collapse of Mt. Gox — Bitcoin Wiki

2014-02-25

Mt. Gox suspends all trading, its website goes offline.

Mt. Gox — Wikipedia

2014-02-28

Mt. Gox files for civil rehabilitation in the Tokyo District Court, disclosing the loss of approximately 850,000 BTC (~$473 million).

Mt. Gox Files for Bankruptcy — NPR

2014-03-20

Mt. Gox announces discovery of 199,999.99 BTC in an old wallet, reducing reported net loss to approximately 650,000 BTC.

Mt. Gox — Wikipedia

2014-04-24

Tokyo District Court converts Mt. Gox proceedings from civil rehabilitation to bankruptcy liquidation.

Collapse of Mt. Gox — Bitcoin Wiki

2015-04-01

WizSec publishes blockchain forensics report concluding most or all missing BTC were stolen from the hot wallet beginning in late 2011.

WizSec: The Missing MtGox Bitcoins

2015-08-01

Mark Karpeles arrested in Tokyo on suspicion of manipulating computer records and embezzlement.

Mark Karpeles — Wikipedia

2018-06-01

Tokyo District Court grants request to convert proceedings back to civil rehabilitation; Nobuaki Kobayashi appointed rehabilitation trustee.

Mt. Gox — Wikipedia

2019-03-14

Tokyo District Court convicts Karpeles of data manipulation (falsifying records to inflate holdings by ~$33.5M); acquits him of embezzlement. Sentenced to 30 months suspended for four years.

Former Mt. Gox Chief Mark Karpeles Acquitted of Most Charges — CNN Business

2020-06-12

Tokyo High Court upholds Karpeles's suspended sentence on appeal.

Japan's High Court Rejects Former Mt Gox CEO's Conviction Appeal — CoinDesk

2023-06-09

DOJ unseals indictment charging Russian nationals Alexey Bilyuchenko and Aleksandr Verner with conspiring to launder approximately 647,000 BTC stolen from Mt. Gox and operating BTC-e.

Russian Nationals Charged — DOJ SDNY

2024-07-05

Mt. Gox rehabilitation trustee begins distributing Bitcoin and Bitcoin Cash to creditors through Kraken, Bitstamp, and BitGo — the first distributions since the 2014 collapse.

Mt. Gox Begins Repaying Bitcoin to Creditors — CNBC

2024-10-10

Trustee Kobayashi announces most repayments to verified creditors completed; repayment deadline extended to October 31, 2025.

Mt. Gox Trustee Announcement — October 10, 2024

2025-03-27

Trustee announces over 19,500 creditors have now received Bitcoin and Bitcoin Cash repayments; additional distributions continue.

Mt. Gox Trustee Announcement — March 27, 2025

2025-10-27

Trustee extends repayment deadline a third time, to October 31, 2026. Approximately 34,000 BTC (~$4B+) remains in estate wallets awaiting distribution.

Mt. Gox Delays Creditor Repayment to October 2026 — CoinDesk

model: claude-code-investigator

generated: 5/8/2026, 2:00:30 AM

last updated: 5/8/2026, 2:42:01 AM

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