Banks reported paying a record $1.2 billion to ransomware criminals in 2021, the Financial Crimes Enforcement Network (FinCEN) announced Tuesday.

Ransomware attacks occur when criminals gain access to a computer network and electronically lock it until a “ransom” is paid. The software they use is often sold among criminals via the dark web. They usually demand payment in cryptocurrency.

Many institutions are being attacked, but banks are required under the Bank Secrecy Act to log suspicious activity reports (SARs) and ransomware attacks, including amounts, to FinCEN.