Court records say he also sent the women anonymous emails telling them he had downloaded nude photos of them. He told them he would publish the images on social media sites if they didn't send him additional pictures or undress for him. If the women complied, Abrahams promised to destroy the images.
At least two of his victims gave in to his demands, authorities said.
"Did you know you were extorting them when you made these demands?" Selna asked.
"Yes," Abrahams responded.
Dressed in matching gray pants and shirt with a black jacket, Abrahams told the judge he has autism and has been under treatment for the past 10 years. He said he was on three medications Tuesday, but he said they wouldn't affect his ability to enter a guilty plea.
Outside court, his attorney Alan Eisner said Abrahams apologizes for his actions, and that the autism played a contributing role in the scheme.
"The social disorder had, certainly, a part in it," said Eisner. "Again, I say that not to blame the conduct on anything, not to make an excuse for the conduct, but that's part of the full picture."
In Wolf's case, Abrahams was able to take nude photos of her without her knowledge, authorities said. He posted a naked photo of Wolf online after she didn't respond to him.
According to an FBI affidavit, Abrahams told Wolf: "Your dream of being a model will be transformed into a porn star."
Wolf, also 19 and a graduate of Great Oak High School in Temecula, won the Miss Teen USA crown in August. She has spoken publically about the incident, saying she would use her fame to highlight cybercrime.
Abrahams is accused of employing similar hacking tactics used by a Florida man who was sentenced to 10 years in prison last year after he broke into the personal online accounts of Scarlett Johansson, Christina Aguilera and other women and posted revealing photos and other material online.