A cryptovirus, cryptotrojan or cryptoworm is a type of malware that encrypts the data belonging to an individual on a computer, demanding a ransom for its restoration.
The term ransomware is commonly used to describe such software, although the field known as cryptovirology predates the term "ransomware".
This type of ransom attack can be accomplished by (for example) attaching a specially crafted file/program to an e-mail message and sending this to the victim.
If the victim opens/executes the attachment, the program encrypts a number of files on the victim's computer. A ransom note is then left behind for the victim.
The victim will be unable to open the encrypted files without the correct decryption key.
Once the ransom demanded in the ransom note is paid, the cracker may (or may not) send the decryption key, enabling decryption of the "kidnapped" files.
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