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Apple said on Thursday that it would strengthen its security measures after a recent episode where hackers broke into the Apple accounts of a number of celebrities, stole their nude photos and leaked them on the Internet.

The company said it would add alerts to tell people about activities that could be signs of a break-in.

Customers will receive emails and alerts called push notifications, which are messages that show up prominently on iPhones and iPads, when someone tries to change the password for their iCloud account, upload their backed-up account data to a new device or log into their accounts for the first time from an unknown device, the company said. The notifications will be added in two weeks.

In the past, Apple customers were receiving emails only when someone changed their account password or logged in from a new device. They received no notification or email when someone loaded an iCloud backup onto another device.

The Wall Street Journal first reported the news in an interview with the company’s chief executive, Timothy D. Cook. A company spokesman declined to comment further than what was stated in the interview.

Over Labor Day weekend, nude photos of celebrities including Jennifer Lawrence and the model Kate Upton spread on the Internet like wildfire. Early news reports pointed to a widespread breach of iCloud, Apple’s online storage service, as a possible source of the leak.

However, Apple earlier this week said that after a 40-hour investigation, the company concluded that there was no breach of its data servers. The company has said it discovered a number of celebrity accounts were compromised by targeted attacks, using methods like phishing or correctly answering security questions to obtain their passwords. It said it was working with law enforcement officials to investigate the case.