The Treasury Department issued its first sanctions against a cryptocurrency exchange on Tuesday as part of a series of actions targeting the use of digital currencies in ransomware attacks.

Tuesday’s sanctions will block all trades involving the cryptocurrency exchange Suex and US entities. According to the Treasury Department, around 40 percent of all Suex transactions involve illegal activities. The department’s Office of Foreign Assets Control (OFAC) is also issuing a new advisory warning that it may issue new sanctions against cryptocurrency exchanges, cyber insurance companies, and other financial institutions that facilitate ransomware payments.

“Ransomware and cyber-attacks are victimizing businesses large and small across America and are a direct threat to our economy,” Treasury Secretary Janet Yellen said in a statement on Tuesday. “We will continue to crack down on malicious actors.”

These new measures are the Biden administration’s most significant move to curb the wave of ransomware attacks that have only become more frequent over the course of the COVID-19 pandemic. In May, one of the US’s largest fuel delivery pipelines, Colonial Pipeline, was taken offline after a cyberattack that requested a ransom. Colonial paid more than $4 million to turn the system back on. That payment was partially recovered by US authorities.

Last year, the Treasury Department issued a pair of advisories warning companies against paying cybercriminals demanding ransoms. The Department reiterated this stance on Tuesday, saying that it would update its ransomware guidance and issue a clear statement opposing ransomware payments.

“As cyber criminals use increasingly sophisticated methods and technology, we are committed to using the full range of measures, to include sanctions and regulatory tools, to disrupt, deter, and prevent ransomware attacks,” Yellen said in a statement Tuesday.