NEW YORK — The circulation of nude photographs stolen from celebrities' online accounts has raised questions about the security of storing information over the Internet.

Apple acknowledged Tuesday that computer hackers broke into the accounts of several celebrities, a security breakdown that Apple blamed on the intruders' ability to figure out passwords and bypass other safeguards.

The affected celebrity accounts were targeted by hackers who had enough information to know the usernames, passwords and answers to personal security questions designed to thwart unauthorized entries, according to Apple. Knowing this crucial information would enable an outsider to break into Apple accounts, including iCloud.

Here is a closer look at how safe data is when stored remotely on these services.

Question: What is the cloud?

Answer: The cloud is a way of storing photos, documents, email and other data on computers located elsewhere, so you're not using space on your computer, phone or other device. Amazon, Apple, Google and Microsoft all offer cloud-based storage.

The advantage is that you can access the same information from any device.

The drawback is that you are putting your information somewhere else, so you run the risk of a hacking attack on those systems and accounts.

Q: Is it secure?

A: For the most part, yes. Companies invest a lot trying to ensure that people's private information stays private.


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"The short answer is the cloud is often more secure than other storage," says Rich Mogull, CEO of security research and advisory firm Securosis.

But that doesn't mean it is completely immune.

"Like a lot of internet services, there are a lot of attackers who have a lot of time," Mogull says.

Q: How can individuals make their data more secure?

A: You need passwords to access your accounts, so choosing a strong one is important.

Tim Bajarin, an analyst at technology research firm Creative Strategies, recommends having different passwords for each account you hold online, so a breach in one system won't compromise another. It is also important to have a number and punctuation mark in each password, or a creative spelling of a word to make it harder to guess. Also, avoid using common words or notable birthdays as passwords. A strong password is particularly important if you store sensitive info.

Q: How can I tell if my phone or computer is uploading information to the cloud?

A: You had to have signed up and agreed to the cloud services' terms of services, but that might have happened long ago, as you were setting up your device.

With iPhone photos, for instance, if you have Photo Stream turned on, that means you are storing your photos on iCloud. On Android phones, check the Auto Backup settings under Google+ in Google Settings.

Q: Will my photos and other information remain on the cloud even after I delete them?

A: They should not. Settings vary for different cloud services, but most of them delete information from the cloud when you delete something from your phone or computer, at least once the device has had a chance to sync with the online service.

All the cloud storage providers have websites you can sign into to check out what information is being stored.

"If you want that extra feeling of being safe, make sure it's deleted online," says technology analyst Patrick Moorhead of Moor Insights & Strategy.

Q: How do I opt out of cloud storage?

A: Check your phone or computer settings if you don't want your photos and documents stored online. There are other ways to store information, including using an external hard drive or your device's own storage.