The US is ramping up its efforts to crack down on shady cryptocurrency mixers. The Treasury Department has imposed sanctions on Tornado Cash, a mixer that allegedly helped launder more than $7 billion in stolen crypto funds since its inception in 2019. Like a previous sanctions target, Blender, Tornado Cash is accused of “indiscriminately” helping thieves by hiding transaction details while failing to institute meaningful anti-laundering safeguards. North Korea’s state-sponsored Lazarus Group hackers are believed to have funneled $455 million through the mixer.

The sanctions block transactions with or for the benefit of Tornado Cash-related individuals and entities, whether they’re located in the US or controlled by Americans. Anyone who detects banned activity is required to inform the Treasury’s Offices of Foreign Assets Control.

Tornado Cash runs on the Ethereum blockchain. Officials said the mixer played a role in other large-scale thefts, including the Harmony Bridge heist (where it laundered $96 million) from June and this month’s Nomad attack (involving “at least” $7.8 million).

The government has taken legal action against crypto mixers for years. Federal law enforcement charged an Ohio man in 2020 for running a darknet mixer that helped criminals launder $300 million. The Treasury only started sanctioning mixers when it blocked Blender this May, however. The US now believes criminal-friendly mixers are a national security threat, and hopes efforts like these will curb both terrorism as well as attempts to dodge conventional sanctions.