The FBI has seized more than $560,000 in cryptocurrency donations intended for Hamas, the Justice Department announced Tuesday as it disclosed an operation disrupting financing for the militant group.

Beyond taking control of cryptocurrency meant to support Hamas' military wing, the department said it had also seized website domains and communication platforms that the group used for fundraising and recruitment. Investigators additionally obtained information on thousands of individuals who had contacted Hamas with the aim of contributing money to the organization.

"My message to Hamas is clear: your networks are not secure, your crypto is vulnerable, and we will not stop until your ability to wage war is defeated," Jeanine Pirro, the U.S. attorney for the District of Columbia, said in a video statement announcing the operation.

According to FBI affidavits filed in connection with the seizures, Hamas began testing virtual currency fundraising in or around early 2019 through its Qassam Brigades, its military wing. The group solicited donations on its Telegram channel and also conducted direct online fundraising. The affidavits state that Hamas officials boasted the currency would be untraceable, and that the group's websites provided instructions on how to make anonymous donations.

That assumption has repeatedly been undercut by law enforcement practice: because blockchain transactions are recorded on public ledgers, U.S. agencies have increasingly relied on blockchain analytics firms to trace illicit funds, and the Treasury and Justice departments have pursued similar crypto seizures tied to Hamas, including sanctioned exchange operators and wallets, in recent years. Providing such donations can also expose contributors to criminal liability, as material support for a designated foreign terrorist organization is a federal crime.

A significant investigative breakthrough came last year, when FBI officials identified a financing network soliciting virtual currency donations for the Qassam Brigades. A confidential source located in the United States alerted law enforcement to a Telegram post requesting contributions to an email address associated with Hamas.

Brett Leatherman, an FBI assistant director in charge of the bureau's cyber division, said the FBI would "continue to use its authorities to intercept illicit funds and prevent terrorist organizations from exploiting digital networks to finance their operations." The seizure of donor contact information, in particular, suggests the operation's impact may extend beyond the funds recovered, though officials have not said whether charges against donors are planned.

Hamas officials could not immediately be reached for comment.

This story was originally featured on Fortune.com.