Web3 cybersecurity team CertiK has identified a significant shift in cryptocurrency laundering methods in 2023. Unlike the previously favored tools such as Tornado Cash, designed to obscure the link between the sender and receiver of assets, an increasing number of cybercriminals, especially those engaged in massive heists, have turned to Bitcoin mixers this year. According to CertiK, "Across the 50 largest exploits of 2023, one-third of stolen proceeds ended up being bridged to or laundered on the Bitcoin network."

In its statistical findings, CertiK reports that nearly $318.4 million was bridged to the Bitcoin network or laundered through BTC, while criminals sent almost three times less money to Tornado Cash. "Excluding funds yet to be moved by exploiters, incidents involving Bitcoin bridging or laundering account for one-third (32.2%) of the total funds stolen," CertiK adds.

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While tools like Tornado Cash are commonly labeled as crypto mixers, they operate differently from authentic Bitcoin mixers. Tornado Cash facilitates the mixing of users&' cryptocurrencies, typically sent to the platform in the form of Ether or ERC-20 tokens, using a smart contract designed to route assets through various addresses. This process aims to eliminate the trace between transaction participants, although there are opinions suggesting potential ways to reconstruct this link.

In contrast, Bitcoin mixers, exemplified by the now-dismantled Sinbad Mixer, function by allowing crypto users to send their assets to a shared pool, where the coins are mixed. Subsequently, the mixed coins are distributed across different wallets. Notably, Sinbad Mixer is built upon the privacy-enhancing protocol known as CoinJoin.

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The increased privacy offered by Bitcoin mixers is not the sole factor driving the shift of cryptocurrency thieves away from Tornado Cash. CertiK emphasizes that "A significant reduction in this contract&'s ETH balance became apparent following the sanction announcement, indicating a change in laundering preferences." Nevertheless, Tornado Cash "remains a channel for smaller-scale laundering."

Similarly, like Sinbad, other Bitcoin mixers such as ChipMixer, Bitcoin Fog, and Helix have been shut down by the United States Department of Justice (DoJ) since 2020.