Cyber Incident Victim: Bitcoin Gold
Date:
Jan 2020
Location:
China
Summary
A cryptocurrency network experienced its second 51% attack, resulting in double-spending exceeding $70,000. The incident involved two deep blockchain reorganizations, with attackers first stealing approximately 1,900 BTG ($19,400) followed by three batches totaling 5,267 BTG ($54,000). The network's vulnerability stemmed from a prolonged decline in hash rate, which significantly reduced security against majority hash power takeovers. This marked a repeat compromise of the same blockchain, highlighting persistent systemic risks.
| CIA Posture | Motives | Tactics, Techniques & Procedures |
|---|---|---|
| Available to members | 1 motive | 1 technique |
| Threat Actors | Type | Location |
|---|---|---|
| 0 actors | Available to members | Available to members |
Description
Bitcoin Gold experienced a 51% network attack on January 16, 2020, resulting in significant double-spending incidents. The attack involved malicious actors gaining majority control of the network's hash rate, enabling transaction reversals and blockchain reorganizations. Two deep reorganizations occurred on January 16 and 17, with the first invalidating transactions totaling 1,900 BTG (approximately $19,400 at contemporary exchange rates). The second reorganization occurred in three distinct batches, compromising 5,267 BTG (approximately $54,000). This brought the total confirmed losses to 7,167 BTG, exceeding $70,000 in value. The attackers exploited Bitcoin Gold's declining hash rate, which had been deteriorating since mid-2018, reducing the computational power required to overpower the network. As a hard fork of Bitcoin using Equihash (144,5) or Zhash algorithms, BTG's security vulnerabilities became apparent through this incident. The attack marked the second 51% compromise in Bitcoin Gold's history, following a previous incident that had already raised concerns about network integrity. No immediate detection mechanisms or mitigation efforts by the Bitcoin Gold development team were detailed in available reports during the attack window.
The double-spend attacks directly undermined trust in Bitcoin Gold's transaction finality and exposed systemic security weaknesses stemming from its diminished hash rate. Financial exchanges and merchants accepting BTG faced elevated counterparty risks during the reorganizations, as previously confirmed transactions were reversed. The incident drew parallels to Ethereum Classic's January 2019 attack, where attackers stole 88,500 ETC ($460,000 at the time), though that case saw partial fund restitution by perpetrators. Bitcoin Gold's market valuation and network participation metrics faced downward pressure following the attack, though specific post-incident price movements or hash rate changes weren't quantified in source materials. The absence of documented protocol upgrades or consensus mechanism changes in response to this second attack left unresolved questions about long-term network security. Blockchain analysts noted the attack demonstrated the heightened vulnerability of smaller proof-of-work cryptocurrencies to hash rate manipulation when mining participation declines.