I was hit by this, or a variant, at my place of business. Hundreds of thousands of files on our shared drive were overwritten, about 2 TB worth of files. Office documents, PDFs, and Adobe documents like PSD and INDD were encrypted. JPEGs were altered but still viewable. All files increased in size by a few hundred bytes.

Pull-only backups were the savior here, although because we didn't notice until the next day, the pulled backups on that system were also overwritten with encrypted/corrupt files. Luckily we had VSS versioning on the pull-only backup location. There was a close call in that the 2 TB or so of "new" data ended up pushing VSS over quota and we almost lost our good versions of the files that way. If not for the VSS versions, we would've had to resort to cold backups which would've been a bit older. As it stood, no file recovered was more than a few hours old.

Auditing on the file share indicates which workstation was infected. Pertaining to that: it surprises me that in 2013, a default install of Windows will not log any useful information about shared folders by default. You must enable object auditing in Group Policy and specifically declare which users or groups are subject to said auditing on a share-by-share basis. In a world without logrotate, I suppose a sensible default is to just let a bunch of shit happen without recording it.

What gets me wound up most of all is the amount of engineering involved for an average home user to protect themselves. I thought a Mac with Time Machine was enough, but a similar virus would easily corrupt those backups if they were available to it over a mapped drive.

It is the goddamn 21st century, and users are still losing work by overwriting documents by accident, or opening a document as an e-mail attachment and not being able to find the actual file they edited. Should people really need an IT guy with ten years of experience to be protected from simple mistakes? Google has made progress on that front with the Chromebook, I suppose.