Cryptography is a technique which is used to hide the original data from unauthorized users. It is used to provide confidentiality, integrity, authentication and security to data. This paper presents the idea of crypto virology which really an opposite side of the cryptography. On the contrary of cryptography, it is offensive in nature. It tells how modern cryptographic paradigms and tools can be used to strengthen, improve and develop new malicious software attacks. It describes a less prominent attack on standalone and networked computer systems known as crypto viral attacks.