Viruses are destructive, but hackers have figured out a way to monetize their elicit activities. Now they hold your data hostage with encryption and a password. This is called Ransomware. Many of these viruses use programs like “bit-locker” and other forms of encryption in an effort to deny you of your data unless you pay. Virus protection is the most valuable tool to protect you from ransomware. You also have to be vary vigilant when opening unknown emails.  
Should I pay the ransom? No. Because most often than not, after you pay you never hear from them again, and your data stays encrypted.  
Here is an example. Someone takes the virus bin or e x e file and simply re-purpose it with his own instructions appear as the solution of payment and contact. Considering the person did not actually write the program, he does not have the password. The intention is to make you believe they do have the password when you pay. Once they have the money they are gone. You password is wrong or you never receive it.  
The best protection is Anti Virus like www.Avast.com and others. Avast has a free version which contains great protection. We are in no way affiliated with Avast, but our office computers use it for protection without any issues.  
How can I recover the data? Unfortunately the best protection is prevention when it comes to these situations. Once encrypted, files cannot be deciphered without the correct password. The passwords for these viruses are about a page long, and 99% of the time the password does not work and was never supposed to.