OAK — OnChain Attack Knowledge

Worked example · 2012-05

Bitfloor exchange hot-wallet compromise — Bitcoin — 2012-09 (reported 2012-09-05)

Loss
approximately 24,000 BTC (~$250,000 at the time) stolen after attackers compromised Bitfloor servers and reached an unencrypted backup of the wallet keys; the coins were virtually all of the exchange's currency reserves [bfregister][bfbitdef].
OAK Techniques observed
OAK-T11.001 (Third-Party Signing Vendor Compromise — primary; the exchange's wallet-server infrastructure was the signing surface; Bitfloor was the custodian, and the custodial hot-wallet operational security was the failure surface — unencrypted backup of wallet keys on a server accessible to the attacker). OAK-T15.003 (Operator Endpoint / Infrastructure Compromise — the attacker gained access to Bitfloor's wallet-server infrastructure via an unsecured server hosting the unencrypted key backup).
Attribution
pseudonymous. Bitfloor founder Roman Shtylman said the breach was his fault: the backup was made after a manual upgrade and he left the keys in an unencrypted area on disk [bfregister]. The attacker's identity was not established in the cited sources.
Key teaching point
Bitfloor is the earliest documented US-based Bitcoin exchange hot-wallet compromise and the canonical 2012 worked example of T8.001 — an unencrypted key backup on an insecure server produced the full hot-wallet drain. The case established the operational security pattern (unencrypted key backup → server compromise → hot-wallet drain) that would recur across the 2013-2016 exchange-hack era (Bitstamp 2015, Bter 2015, Bitfinex 2016) until cold-storage and hardware-security-module (HSM) architectures became standard.
Corrected 2026-10-11
Date moved from 2012-05-02 to September 2012 (reported 2012-09-05); removed the unsupported single-transaction, 'fourth-largest', repayment-pledge and 2013 bank-closure claims; the cause is per Shtylman an unencrypted key backup left on disk after an upgrade.

Summary

Bitfloor was a US-based Bitcoin exchange run by Roman Shtylman. It was one of the earliest Bitcoin-fiat exchanges serving US customers and was a US-based Bitcoin exchange.

In early September 2012 (reports date from 2012-09-05), attackers compromised a few Bitfloor servers and reached an unencrypted backup of the wallet keys, losing approximately 24,000 BTC, virtually all of the exchange's currency reserves [bfregister]. Earlier text dated this 2012-05-02; sources found date it September 2012.

The cited sources do not say how many transactions were used.

Bitfloor paused exchange operations after the loss; US dollar accounts and trade records were unaffected, and Shtylman warned that he might have to shut the exchange down fully and begin repaying accounts if no other option worked [bfregister]. Earlier text on later resumption, repayment commitments and a 2013 shutdown after a bank closure was not supported by the sources found and has been removed.

The incident is the earliest-documented US-exchange hot-wallet compromise involving unencrypted key backup as the load-bearing operational security failure, establishing the T8.001 pattern that would recur across the exchange ecosystem for the next five years until cold-storage architectures (multi-signature, HSM-backed signing, geographically distributed key shards) became industry standard.

Timeline (UTC)

When Event OAK ref
2011–2012 Bitfloor operates as a US Bitcoin exchange; majority of user funds held in hot wallet; wallet keys backed up unencrypted to a server T8.001 (standing surface)
2012-09 Attacker compromises Bitfloor's wallet-server infrastructure; discovers unencrypted key backup; extracts hot-wallet signing keys T15.003 (infrastructure compromise) + T8.001 (unencrypted key backup)
2012-09 ~24,000 BTC drained [bfregister] T11.001 (signing-infrastructure compromise)
2012-09-05 Press reports the breach; exchange operations paused [bfregister] (incident response)

Realised extraction

Approximately 24,000 BTC (~$250,000 at the time) [bfregister]. Recovery and repayment outcomes are not established in the cited sources.

Public references

Techniques demonstrated (2)