A new warning from the FBI and other federal officials warns that ransomware software from Medusa is on the rampage, targeting computer users via their emails for extortion.

Federal agencies are warning Gmail and Outlook email users of a costly ransomware scheme that has already affected more than 300 victims. The FBI and the U.S. Cybersecurity and Infrastructure Security Agency issued the advisory, detailing a warning about the Medusa hacking organization, which has been active since 2021.

The agencies warn Gmail and Outlook users to be on the outlook for harmful emails containing ransomware — a kind of malicious software that prevents you from accessing your computer files, systems or networks and demands you pay a ransom for their return.