Cryptovirology is known as the younger evil sibling of Cryptography. It is a field devoted to the study of using cryptography for designing powerful malicious software. It was observed that Public-key Cryptography can be used to break the symmetry between what an antivirus analyst sees: regarding what the virus writer sees. The former only sees a public key whereas the latter sees public key and a corresponding private key. ‘Cryptoviral Extortion’ was the first attack identified in the field of cryptovirology. In this attack, a virus, worm or hybrid encrypts the victim’s files and the user must pay the malware author to receive the needed session key (which is encrypted under the author’s Public key that is contained in the malware) if the user does not have backups and needs the files back.