Pierluigi Paganini January 24, 2023

The U.S. FBI attributes the $100 million cyber heist against Harmony Horizon Bridge to North Korea-linked Lazarus APT.

The U.S. Federal Bureau of Investigation (FBI) this week confirmed that in June 2022 the North Korea-linked Lazarus APT group and APT38 stole $100 million worth of cryptocurrency assets from the Blockchain company Harmony Horizon Bridge.

“The FBI continues to combat malicious cyber activity, including the threat posed by the Democratic People’s Republic of Korea (DPRK) to the U.S. and our private sector partners. Through our investigation, we were able to confirm that the Lazarus Group and APT38, cyber actors associated with the DPRK, are responsible for the theft of $100 million of virtual currency from Harmony’s Horizon bridge reported on June 24, 2022.” reads the report published by the FBI.

The company reported the incident to the authorities, the FBI started investigating the cyber heist with the help of several cybersecurity firms. 

Harmony’s Horizon Bridge allows users to transfer their crypto assets from one blockchain to another, the company immediately halted the bridge to prevent further transactions and notified other exchanges.

The blockchain security firm CertiK published a detailed analysis of the incident, it confirmed that the threat actors were able to access the owners of Horizon’s multiSig wallets, then drained the funds from Harmony.

“On June 23, 2022 at 11:06:46 AM +UTC, the bridge between Harmony chain and Ethereum experienced multiple exploits. Our expert analysis has identified twelve attack transactions and three attack addresses.” reads the analysis published by CertiK. “Across these transactions the attacker netted various tokens on the bridge including ETH, USDC, WBTC, USDT, DAI, BUSD, AAG, FXS, SUSHI, AAVE, WETH, and FRAX. The transactions vary in value but range from $49,178 to upwards of $41,200,000. The attacker accomplished this by somehow controlling the owner of the MultiSigWallet to call the confirmTransaction() directly to transfer large amounts of tokens from the bridge on Harmony, which led to a total loss around $97M worth of asset on the Harmony chain which the attacker has consolidated into one main address.”

On June 27, the threat actors behind the cyber heist culprit have begun transferring the funds (roughly $39 million) through the Tornado Cash mixer service to launder the illicit profits.

The blockchain security firm Elliptic was able to analyze the transactions even after the use of the mixer service, it first reported that the North Korea-linked Lazarus APT was behind the attack.

“There are strong indications that North Korea’s Lazarus Group may be responsible for this theft, based on the nature of the hack and the subsequent laundering of the stolen funds. Lazarus is believed to have stolen over $2 billion in cryptoassets from exchanges and DeFi services.” reads the report published by Elliptic. “The theft was perpetrated by compromising the cryptographic keys of a multi-signature wallet – likely through a social engineering attack on Harmony team members. Such techniques have frequently been used by the Lazarus Group.”

According to the firm the threat actors compromed the cryptographic keys of a multi-signature wallet, likely through a social engineering attack aimed at Harmony team members.

Elliptic researchers pointed out that the relatively short periods during which the stolen funds stop being moved out of Tornado cash are consistent with nighttime hours in Asia-Pacific time zone.

The FBI experts reported that on January 13, 2023, North Korean threat actors used the RAILGUN privacy protocol to launder over $60 million worth of ethereum (ETH) stolen during the June 2022 cyber heist. Then the threat actors sent a portion of the stolen funds to several virtual asset service providers and converted them to bitcoin (BTC).  

The good news is that part of these funds were frozen, in coordination with the virtual asset service providers. The remaining bitcoin subsequently moved to a number of addresses shared by the FBI in its report.

The FBI also revealed that the attack leveraged the malware TraderTraitor campaign in the Harmony intrusion.

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Pierluigi Paganini

(SecurityAffairs – hacking, Harmony)

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