US. Based Cryptocurrency firm Harmony has faced a cyber attack, as hackers stole $100 Mn in digital assets off of Harmony’s Horizon crypto bridge. The form confirmed the attack via a series of tweets.

“The Harmony team has identified a theft occurring this morning on the Horizon bridge amounting to approx. $100MM. We have begun working with national authorities and forensic specialists to identify the culprit and retrieve the stolen funds,” the company said in a tweet.

In a separate tweet, Harmony confirmed that it’s bitcoin bridge has not been impacted by the attack, and that “Its funds and assets stored on decentralized vaults are safe at this time.”

As the reports came out, Harmony’s native token ONE slumped by 12%, despite the market wide recovery as bitcoin climbed back up to $21,000 after falling below the crucial $20,000 mark.

The Horizon bridge, like many other crypto bridges, allows crypto/NFT holders to transfer their assets from one blockchain network to another. These bridges have various use cases. Some blockchain networks are faster/safer/cheaper. Others offer features like lending and borrowing on platforms like Aave. Horizon operates in a more centralised way, with a pool of validators approving transfers. When a token is locked on a blockchain, Horizon’s validators validate the lock action and relay the information to the bridged blockchain, where a matching amount of bridged token is minted. Horizon caters to Harmony’s own blockchain, Ethereum Blockchain and Binance Smart Chain (BSC).

Tokens including Wrapped Ethereum (WETH), AAVE, SUSHI, DAI, Tether (USDT) and USD Coin (USDC) have been stolen from the bridge and swapped for Ethereum.

Meanwhile, harmony has stopped any further transactions on Horizon Bridge and informed exchanges of the attack. “The team is all hands on deck as investigations continue,” they added.

This attack adds to the list of multiple attacks on cryptocurrency bridges in recent times. The Ronin Network saw a breach of $635 Mn in March, while Wormhole bridge was attacked for $326 Mn in February.