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2026 Proof of Custody. Published by Onramp Bitcoin. Editorial Independence.PrivacyTermsproofofcustody.io
The timeline
ExchangeMay 2024The Infrastructure Era

DMM Bitcoin

An employee at the exchange's wallet-infrastructure provider was social-engineered, and stolen session credentials were used to manipulate a legitimate transaction request.

By Steve L, Editorial Lead·Reviewed by Proof of Custody Editorial
Published Aug 3, 2026
Reported loss
4,502.9 BTC

~$305 to 308M. The exchange subsequently wound down.

What it should change

Your custody is only as strong as every vendor in the signing path, including the ones you have never heard of.

Which setups this class of failure could reach

These are the custody configurations structurally exposed to this kind of event. It describes the failure class, not any individual holder.

Bitcoin left on an exchange

Whether your own arrangement sits in one of those groups is the question our Custody Independence Standard is designed to answer, and the four questions in Is your custody setup actually safe? walk through it.

Sources

FBI, DC3 and Japan NPA joint advisory

Figures are as reported by the named sources. Proof of Custody has not independently reproduced the underlying analysis.

← Earlier
Prime Trust
2023
Later →
WazirX
July 2024
How to cite
Proof of Custody, "DMM Bitcoin" incident record, proofofcustody.io/incidents/dmm-bitcoin-2024
Frequently asked questions
What happened to DMM Bitcoin?+

An employee at the exchange's wallet-infrastructure provider was social-engineered, and stolen session credentials were used to manipulate a legitimate transaction request. Reported loss: 4,502.9 BTC.

What should DMM Bitcoin change about how I hold bitcoin?+

Your custody is only as strong as every vendor in the signing path, including the ones you have never heard of.

Which custody setups were exposed to the DMM Bitcoin failure?+

This class of failure could reach: bitcoin left on an exchange. It describes the failure class rather than any individual holder.

See the full timelineAssess your own setup