What Is Ransomware ?

Ransomware is a type of computer virus that infects a target computer, encrypts their sensitive documents and files, and locks the out until the victim pays a ransom amount, most often in Bitcoins.

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There are two types of Ransomware which we know

File encryptor ransomware
Encrypts personal files/folders 
(e.g., the contents of your My Documents folder - documents, spreadsheets, pictures, videos).  
Files are deleted once they are encrypted and generally there is a text file in the same folder as the 
now-inaccessible files with instructions for payment.  
You may see a lock screen but not all variants show one.  Instead you may only notice a problem when you attempt to open your files. 
This type is called 'file encryptor' ransomware. For example, CryptoLocker is a file encryptor 

WinLocker
'Locks' the screen (presents a full screen image that blocks all other windows) and demands payment.  No personal files are encrypted.  Example screenshots of with type running on a computer are shown below 
(click for larger view)..  This type is called 'WinLocker' ransomware.

Sometimes even the best security experts aren't able to unlock them and end up paying off ransom to crooks in order to get their important files back.

Wikipedia :

1. Ransomware is a type of malware that restricts access to the computer system that it infects, and demands a ransom paid to the creator(s) of the malware in order for the restriction to be removed.

Below Images Are Example of Ransomware virus