How Hackers Targeted Celebrities' Apple Accounts

— -- Hackers gained access to leaked nude photos purporting to be of dozens of A-list celebrities by an "all too common" tactic, according to Apple.

"After more than 40 hours of investigation, we have discovered that certain celebrity accounts were compromised by a very targeted attack on user names, passwords and security questions, a practice that has become all too common on the Internet," Apple said in a statement today.

The targeted celebrities included Jennifer Lawrence and Kate Upton, and their purported photos were leaked online late Sunday.

The investigation found that none of the leaked photos were the result of any breach of Apple's systems, including iCloud and Find My iPhone, the company noted in its statement.

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Apple said it is "continuing to work with law enforcement to help identify the criminals involved."

The FBI said on Monday it is "aware" that someone has leaked nude photos purporting to be pictures of a dozen Hollywood starlets.

Apple immediately released a statement saying it takes any breach of user privacy seriously and would actively investigate the report.

ABC News' Rebecca Jarvis and Neal Karlinsky contributed to this report.