LOS ANGELES (AP) -- The FBI and the U.S. Cybersecurity and Infrastructure Security Agency are warning against a dangerous ransomware scheme.

In an advisory posted earlier this week, government officials warned that a ransomware-as-a-service software called Medusa, which has launched ransomware attacks since 2021, has recently affected hundreds of people. Medusa uses phishing campaigns as its main method for stealing victims' credentials, according to CISA.

To protect against the ransomware, officials recommended patching operating systems, software and firmware, in addition to using multifactor authentication for all services such as email and VPNs. Experts also recommended using long passwords, and warned against frequently recurring password changes because they can weaken security.

Medusa developers and affiliates -- called "Medusa actors" -- use a double extortion model, where they "encrypt victim data and threaten to publicly release exfiltrated data if a ransom is not paid," the advisory said. Medusa operates a data-leak site that shows victims alongside countdowns to the release of information.

"Ransom demands are posted on the site, with direct hyperlinks to Medusa affiliated cryptocurrency wallets," the advisory said. "At this stage, Medusa concurrently advertises sale of the data to interested parties before the countdown timer ends. Victims can additionally pay $10,000 USD in cryptocurrency to add a day to the countdown timer."

Since February, Medusa developers and affiliates have hit more than 300 victims across industries, including the medical, education, legal, insurance, technology and manufacturing sectors, CISA said.