At least two nude photos of the 26-year-old actress have surfaced on the Internet. Both photos appear to be self-taken by the woman who strongly resembles Johansson.
The FBI wouldn't discuss any specifics of the case, but confirmed to Eyewitness News they are "investigating a person or groups responsible for the series of computer intrusions of high-profile figures in Los Angeles."
Entertainment news website TMZ is reporting that as many as 50 celebrities were hacked, including Jessica Alba, Christina Aguilera, Miley Cyrus, Demi Lovato and Vanessa Hudgens.
Mila Kunis is reportedly also a victim of hackers. TMZ reports that four photos were taken from the actress's cellphone, including two of her "Friends with Benefits" co-star, Justin Timberlake.
In one photo, Timberlake is shirtless. In another, he jokingly is wearing pink women's underwear on his head.
Attempts to contact Johansson and Kunis were not returned.
"The Norton crime report just came out saying 10 percent of people globally experience some kind of cybercrime that involves their cellphone," said Kevin Haley, an online security specialist.
Online security experts say the best way to protect personal information on a cellphone is to change the default password.
It may sound obvious, but they say many people forget or are unaware to do it.
"Everyone knows what the default password is for all the different carriers, so it's very, very simple for them to break in," he said.
Or as TV personality Nick Cannon said Wednesday: "Why are you taking pictures naked anyway?"