Honolulu police and CrimeStoppers are warning about an email extortion scam that threatens to release secretly recorded videos of victims.

CrimeStoppers said in a news release that victims have received a message saying a hacker compromised their computer and used their webcam to record a video of them while they were viewing “inappropriate material” on the internet.

The hacker then threatens to release the video to the victim’s contacts unless he or she pays a Bitcoin ransom.

CrimeStoppers urged the public not to open any attachments from strangers and to consider turning off computer cameras and covering them when they are not in use.

Anyone who receives such messages is asked to call police.