Funds From $100M Horizon Bridge Exploit Sent to Tornado Cash Mixing Service

  • Thieves appear to be trying to launder funds with move of $35 million stolen from the cross-chain bridge
  • Stewards of the bridge, Harmony, offered a $1 million bounty in exchange for returning the stolen funds but has so far received no response

Around a third of the $100 million stolen last week from Horizon Bridge, a cross-chain interoperability platform between Ethereum, Binance Smart Chain (BSC) and Harmony blockchain networks, has been transferred to an address belonging to crypto mixing service Tornado Cash.

According to a Sunday tweet thread from Peckshield — the bridge’s security auditor — around 30,000 ether ($35.4 million) are currently on the move in what appears to be an attempt to conceal the provenance of the stolen funds.

Peckshield did not immediately respond to attempts by Blockworks to confirm details of the transfer. Last week’s hack saw more than $98 million in various tokens siphoned off the Horizon Bridge platform and subsequently swapped to ether.

Stewards of the bridge, Harmony, said in an updated blog post Sunday they were aware the hacker had begun moving funds through Tornado Cash and were reviewing various options for users and partners.

“Transparency is important in blockchain and we aim to be transparent with our community but we ask the community to remain patient during this investigation and confidentiality at this time,” Harmony said in its post.

Mixers or tumblers, such as Tornado Cash, are services providing users the ability to conceal the transaction history of certain cryptocurrencies by pooling and mixing them together with other users’ funds.

The team at Harmony had offered a $1 million bounty for the return of the funds on Friday and had advocated for no criminal charges to be laid, though the call remains unanswered.

“The desire to work with the hacker remains but we will continue the full investigation until resolution or the funds are returned,” Harmony said Monday.

In the post, which has been updated regularly since the hack took place last week, Harmony said its incident response team found no evidence of any breaches in its smart contract codes nor to the Horizon platform.

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  • Sebastian Sinclair


    Senior Reporter, Asia News Desk

    Sebastian Sinclair is a senior news reporter for Blockworks operating in South East Asia. He has experience covering the crypto market as well as certain developments affecting the industry including regulation, business and M&As. He currently holds no cryptocurrencies. Contact Sebastian via email at [email protected]