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Criminals more reliant on cross-chain bridges than ever after mixer crackdowns

The sanction of cryptocurrency mixer Tornado Cash in August caused the first major shift, but that is now accelerating even faster than projected.

Cybercriminals have accelerated their shift away from crypto mixers for cross-chain bridges over the past year, according to blockchain forensics firm Elliptic.

In June and July, nearly all of the crypto stolen was laundered through cross-chain bridges, Elliptic’s data shows a complete reversal from the first half of 2022.

In a Sept. 18 blog post, Elliptic explained the cross-chain crime trend is due to the “crime displacement” effect — where criminals move to a new method to carry out the illicit activity when the existing method gets over-policed. However, the shift to cross-chain bridges is rising ahead of their projections. 

Proportion of funds laundered between cryptocurrency mixers and cross-chain bridges between January 2022 and July 2023. Source: Elliptic.

Between July and September 2022, the ratio of laundered funds passing through mixers vs. cross-chain bridges flipped, corresponding to the U.S. Office of Foreign Asset Control’s sanctioning of Tornado Cash in August 2022, said the firm.

Elliptic said many cybercriminals, like the North Korean-backed Lazarus Group, flocked to the Avalanche bridge after the sanctions.

This same bridge was reportedly used recently by the Lazarus Group to facilitate some of the stolen funds in Stake’s $41 million exploit on Sept. 4, according to blockchain security firm CertiK.

Crypto mixers saw a small comeback between November 2022 and January 2023, due to the shutdown of RenBridge — which closed in December after its financer, Alameda Research collapsed from FTX’s bankruptcy.

Elliptic estimates that RenBridge facilitated $500 million in laundered funds throughout its operation.

However, shortly after, criminals have moved back to cross-chain bridges again, even more than before.

Related: 3 steps crypto investors can take to avoid hacks by the Lazarus Group

Elliptic said that criminals may be preferring cross-chain bridges as it is difficult for blockchain forensic firms to track illicit activity across chains in a scalable manner.

“Criminals are aware that legacy blockchain analytics solutions do not have the means to trace illicit blockchain activity across blockchains or tokens in a programmatic or scalable manner.”

In addition, many of these stolen tokens are only exchangeable through cross-chain bridges, while most of these DeFi services do not require identity verification to use, Elliptic explained.

The firm estimates that $4 billion in illicit or high-risk cryptocurrencies have been laundered through cross-chain bridges since 2020.

Magazine: $3.4B of Bitcoin in a popcorn tin — The Silk Road hacker’s story

Bitwise’s Bitcoin and Ethereum ETF clears first SEC hurdle

OFAC-compliant blocks on Ethereum hit three-month low of 47%

Back in November, the percentage of Ethereum blocks complying with orders from the Office of Foreign Asset Control peaked at 79%.

The percentage of Ethereum blocks complying with orders set by the United States Office of Foreign Asset Control (OFAC) has now fallen to 47% — the lowest level since Oct. 11. 

The latest milestone in reversing censorship comes nearly three months after the percentage of OFAC-compliant blocks peaked at 79% on Nov. 21.

OFAC-compliant blocks are those that exclude transactions involving parties sanctioned by the U.S. Treasury Department’s Office of Foreign Assets Control.

A fall in compliant blocks could be seen as a win for those who oppose censorship within the Ethereum ecosystem.

Percentage of OFAC-compliant blocks following the Ethereum Merge on Sept. 15. Source. MEV Watch.

Blockchain consulting firm Labrys, the creator of MEV Watch, said in a statement thathe fall may be attributed to more validators opting to use MEV-boost relays that do not censor transactions in accordance with OFAC requirements.

“In particular, the BloXroute Max Profit relay, Ultrasound Money relay and Agnostic Boost relay have picked up most of the change in market share.”

MEV-boost relays act as trusted mediators between block producers and block builders, which enables Ethereum validators to outsource their block production to other block builders.

Lachlan Feeney, the CEO of Labrys, said in a Feb. 14 statement that he’s happy with how the Ethereum community has responded to the censorship issue since it first surfaced post-Merge.

He noted the recent fall in censorship-compliant blocks was particularly notable given it was achieved without a user-activated soft fork (UASF). He noted that “many members” of the Ethereum community had called for the soft fork prior to the Merge to combat censorship.

“I am incredibly proud of the Ethereum community for the progress we have made with this issue,” said Feeney, adding:

“When we released the MevWatch tool drawing attention to a flaw within Ethereum, the community did not stick its head in the sand but instead rose to the occasion and made significant progress addressing the issue.”

However, “there is still more work to be done,” Feeney stressed.

Related: Ethereum at the center of centralization debate as SEC lays claim

OFAC most notably sanctioned Ether (ETH) and USD Coin (USDC) wallet addresses that transact using the Ethereum-based privacy mixing tool Tornado Cash on Aug. 8.

A visualization of the last 100 blocks showing which are OFAC-compliant. Source. MEV Watch

After the first 24 hours of Ethereum under its new proof-of-stake consensus mechanism on Sept. 16, only 9% of blocks were OFAC-censored. 

However this figure sharply increased over the next two months, peaking at 79% on Nov. 21.

The percentage of OFAC-compliant blocks then hovered around the 68-75% range until Jan. 29 when it was 66%. Since then, it has steadily decreased despite a few minor spikes.

Bitwise’s Bitcoin and Ethereum ETF clears first SEC hurdle