This is how fast things change in technology: Some advice I gave two weeks ago is obsolete.

It involved "ransomware," a type of malicious software that encrypts PC files so that they can't be read, then demands hundreds of dollars in ransom be paid to anonymous online hackers to unlock the files. I wrote (tinyurl.com/nxua6u7) that the victim had already paid the ransom to the hackers, and I said that there'd been no other choice.

Why? Up to that point, PC security software didn't prevent and hadn't been able to fix ransomware infections, which are caused by clicking on links to malicious websites disguised as legitimate ones. (Some smartphone security software does prevent infections; see tinyurl.com/m9f36or)

But George Trezac, a reader in Lakeland, Fla., pointed out that a new solution to PC ransomware appeared about the same time as my column. Well-known California security firm FireEye Inc. and European security firm Fox-IT began offering free software that helps victims of CryptoLocker, the best-known ransomware, to unlock their encrypted files without paying a ransom (see details at tinyurl.com/ml69lvs). The unlocking software is based on information gained in June when the FBI and others raided Internet servers using the CryptoLocker software (see tinyurl.com/nbdxqoh).

This is a major win for consumers. The Register, a technology publication, reported that since late 2013 CryptoLocker has affected 545,000 computers worldwide, about half of them in the U.S. Victims have paid about $27 million in ransom to get their files unlocked (see tinyurl.com/pnp9rch). Those who didn't pay lost access to their files.

To use the file-unlocking method, a consumer uploads a file encrypted by hackers along with an e-mail address to the security firms' website (see above). The consumer is then e-mailed a software key and a link to a downloadable recovery program. Using the key and recovery program together unlocks all of a consumer's PC files that have been illicitly encrypted.

Q: I've arranged photos on my iPad into albums. To reduce clutter, I deleted pictures from my "camera roll" that I had put into albums, only to find that the pictures disappeared from the albums, too. Is there a way to delete photos without also deleting them from the albums?

Marilyn Signer, Lakeland, Fla.

A: When you delete photos from an iPad or iPhone, remember that there is just one copy of each picture. The different image categories that came with your iPad — "photos," "camera roll," "panoramas" and "videos" — are all sharing the same picture collection. Deleting a picture from any of these categories erases the only copy.

The new picture albums you've created behave differently. A picture that's deleted from a new album isn't deleted from the iPad.

The iPad photo "stream" also operates differently. It consists of pictures that you've uploaded to Apple's iCloud online service so they can be viewed by others. You can delete pictures from the online stream without affecting the originals on your iPad.

E-mail tech questions to steve.j.alexander@ gmail.com or write to Tech Q&A, 425 ­Portland Av. S., ­Minneapolis, MN 55488. Include name, city and telephone number.