The FBI is warning that cybercriminals are hacking into the social media accounts of adults and children to steal their intimate explicit images and videos.

The perpetrators rely largely on social engineering tactics to target people, the alert said, and victims are often extorted, or their stolen content published online.

“Victims often face re-victimization through harassment, sextortion, stalking or other targeted attacks, such as advertising stolen content on a victim’s own social media page,” the FBI wrote.

These types of crimes have been known for years. But the FBI’s public alert could indicate that these incidents are now on the rise, according to Rachel Tobac, the CEO of the security awareness training firm SocialProof Security.

Tobac said that these attacks especially target young boys, and that these attacks are “a big public health issue,” given that sometimes the victims are driven to self-harm in response.

When reached, the FBI did not comment but referred TechCrunch to a press release, in which the bureau said it “has determined that student-athletes are frequently targeted due to their public profiles.”

The FBI’s advisory said the attackers rely on brute-forcing accounts using leaked or previously used passwords, impersonating customer service representatives by pretending to work for Instagram and other social media companies, and contacting targets alleging that they need to recover their account. Some hackers use phishing emails that rely on fake domains that look like legitimate social media login pages.

To protect yourself, use unique passwords stored in a password manager, ensure multi-factor authentication is switched on, and be suspicious of anyone reaching out unprompted claiming to work for a social media company, as tech companies generally do not reach out to their customers. The FBI urges people to avoid storing intimate pictures in online accounts.

Updated with response from FBI.