CryptoWall continues and expands upon CryptoLocker. Both are ransomware, and both rely on phishing techniques to lure someone into clicking on a link. Download the software and all data on the drive, or any mapped drives, gets encrypted. The criminal enterprise behind the malware will now sell you the decryption key through Bitcoin, and unfortunately businesses and individuals will pay because it's cheaper and faster. Here's a horror story from Network World (opens in new window). The firm in question had their entire data store encrypted, and even with payment it took 18 hours to get back online. One of their databases was corrupted so that had to be restored with the concomitant loss to productivity.
So, even payment has a cost.
It's an Internet updated protection racket: "nice files you have there, be a shame if something happened". How do infections occur? Email attachment, drive-by downloads from a hijacked legitimate site, and adware. How do I protect myself and my network? Always patch, always update, always have current anti-virus protection- and safe surfing. Restrict administrative rights, and don't map drives to network shares in the admin profile. Don't click on links in emails, and be wary of attachments. Right-click and scan downloads and attachments before you open them.
TechRepublic has a good article as well (opens in new window).
CryptoWall is another reminder that a lot of scams and crimes haven't changed through the years- just the delivery method. Criminals and con men always look for the human vulnerability first. Kevin Mitnick was a hacker, sure, but his main success came from calling up bank employees, saying he was from security, and asking them for their password. Who wouldn't want to help be more secure? And the bank examiner scam- targeting someone outside a bank, posing as law enforcement, and enlisting the unwary but helpful citizent to catch a maleficent teller, hits on two urges: wanting to help the law, and having a secret.
So, beware, backup and test your restores, have a local and a cloud backup, stay updated, and be careful.