The changes, for later this year, raised concerns that the company is installing surveillance technology that governments could exploit.
The software, which will reportedly be called the “NeuralMatch” will compare images on a person’s iPhone with images on the U.S. law enforcement’s child sexual abuse database, and if it flags enough child abuse images, a review will start.
Law enforcement will be alerted if reviewers find there is evidence the photos are illegal.
The system would be able to check the photos stored on the iPhone before they are uploaded to iCloud servers.
Apple unveiled plans to scan U.S. iPhones for images of child sexual abuse, drawing applause from child protection groups but raising concern among some security researchers that the system could be misused, including by governments looking to surveil their citizens.
The tool designed to detected known images of child sexual abuse, called "NeuralMatch," will scan images before they are uploaded to iCloud. If it finds a match, the image will be reviewed by a human.
If child pornography is confirmed, the user's account will be disabled and the National Center for Missing and Exploited Children notified.
Apple said it had designed the new features in a way that protected the privacy of users, including by ensuring that Apple will never see or find out about any nude images exchanged in a child’s text messages.
The scanning is done on the child’s device, and the notifications are sent only to parents’ devices. Apple provided quotes from some cybersecurity experts and child-safety groups that praised the company’s approach.
Other cybersecurity experts were still concerned. Matthew D. Green, a cryptography professor at Johns Hopkins University, said Apple’s new features set a dangerous precedent by creating surveillance technology that law enforcement or governments could exploit.
“They’ve been selling privacy to the world and making people trust their devices,” Mr. Green said. “But now they’re basically capitulating to the worst possible demands of every government. I don’t see how they’re going to say no from here on out.”