Story highlights Christopher Chaney will plead guilty to nine counts

Victims include Scarlett Johansson and Mila Kunis

Chaney has said he was "addicted" to hacking celebrities' e-mail accounts

A Florida man who said he became "addicted" to hacking into e-mail accounts, including those of celebrities Mila Kunis and Scarlett Johansson, will plead guilty Monday to nine counts, according to court documents.

Christopher Chaney, 35, of Jacksonville, said he started hacking as a curiosity and it "snowballed." He said he "didn't know how to stop."

"I deeply apologize. I know what I did was probably one of the worst invasions of privacy someone could experience," Chaney told CNN affiliate WAWS/WTEV in Jacksonville, Florida, in October 2011.

According to a plea agreement released Thursday, Chaney faces up to 60 years in prison on federal charges that include unauthorized access and damage to a protected computer and wiretapping. He also could be fined $2.25 million and ordered to pay restitution.

Chaney was accused of hacking into e-mail accounts and devices belong to more than 50 people, including entertainers Christina Aguilera, Simone Harouche and Renee Olstead, prosecutors said.

"Mr. Chaney has from the onset of these charges maintained that he would accept responsibility for any crimes he may have committed," defense attorney Christopher Chestnut said in a statement to CNN on Friday. "He is honoring that commitment on Monday with a change of plea. He remains remorseful for harms that may be been caused to those named in the charging document. He is now seeking a reasonable sentencing commensurate with the crimes charged."

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Chaney allegedly accessed nude photos of some of the celebrities during the hacking, and a circulated nude photo of Johansson was part of the federal investigation, prosecutors said.

Chaney also used public sources to mine data about his victims, which included both males and females, all associated with the entertainment industry, authorities said.

Authorities allege that once Chaney hacked into a celebrity's e-mail account, he would use the contact lists to find other celebrities' e-mail accounts. This allowed him to add new victims, authorities charge.

Authorities allege that Chaney distributed photos of the celebrities that he obtained illegally and offered them to various celebrity blog sites, but he didn't seek money in exchange.

Some of the illegally obtained files, including private photographs, were ultimately posted online "as a result of Chaney's alleged activities," authorities said in a statement issued last year.

Chaney initially faced 26 criminal counts.