"Knowing those photos were deleted long ago, I can only imagine the creepy effort that went into this. Feeling for everyone who got hacked."
The scale of the breach became apparent on Sunday when users of the 4chan message board, a diverse online community that has been criticized in the past for misogyny, began sharing pictures.
Some more mainstream news and entertainment sites took up the story -- and some linked to the images before taking them down amid legal threats and public outrage.
According to a report on news and gossip site Gawker, users of a AnonIB -- an anonymous photo-sharing platform -- have been boasting of a hack since last week.
Some users, hiding behind pseudonyms, made an apparent attempt to sell the pictures or to trade them with fellow hackers for others.
Tech news site The Next Web reported what it said was evidence that hackers had found a weakness in Apple's "Find my iPhone" service, an app that tracks lost or stolen handsets.
Apple has patched the alleged hole, the report said, but not before news of it spread in the hacker community, perhaps allowing unscrupulous strangers to access private online data.
But other reports suggested that the pictures could have been collated from multiple sources, perhaps not including iCloud at all, and may have been gathered over several years.
News site Deadspin said it had been contacted in early August by a source claiming he had been offered the pictures for sale.
The scale of the hack, and the targeting of women in the public eye, quickly revived the debate on social media about privacy concerns and about misogyny on the Internet.
The scandal also posed a public relations challenge to tech companies, who have been marketing online storage like iCloud, DropBox or GoogleDrive as a safe haven for users' private data.
Several popular tech blogs marked the story by providing advice on storing private data safely, by using advanced encryption and two-step password identification or by keeping it offline.