Really nasty. That is what it is.
This malicious software (malware) has been spreading through fake emails that disguise themselves as coming from legitimate companies such as FedEx or UPS. The malware has the ability to find and encrypt files you have access to no matter where they are located: shared network drives, USB drives, external hard drives, network file shares and even some cloud storage drives. If one computer on a network becomes infected, all other computers on that network run the risk of being infected as well.
What about getting your information back? Unless it is backed up on an external drive that is not hooked up to your network or computer, odds are your information is gone. There is no way to decrypt your files either, seeing as the hackers have the key needed to decrypt them. While victims are told they have three days to pay the attacker through a third-party payment method (MoneyPak, Bitcoin), some victims have claimed online that they paid the attackers and did not receive the promised decryption key. A good idea is to not pay the attackers and seek immediate assistance.
What to do if you have already been infected?