Christopher Chaney, who hails from Florida, appeared in a federal court on Monday (March 26), pleading guilty to nine offences including wiretapping and unauthorized access to a computer. He has been remanded in custody.
Chaney, who is currently unemployed, was reported last week to have negotiated a plea deal. He originally pleaded not guilty to 26 offences at a pre-trial hearing.
The 35-year-old was arrested in October following an investigation when leaked nude photographs of Avengers star Johansson appeared on the internet, and was quoted as saying that his actions started as "a curiosity".
Chaney will be sentenced on July 23 and could face up to 60 years in prison. He may also have to pay a fine of up to $2 million (£1.25 million) and restitution of between $15,000 and $400,000 to each of his victims.
In deciding to hold Chaney in custody, the sitting district judge said that he had continued to hack into celebrity e-mail accounts even after his arrest and subsequent interview by the FBI.