Computer virus is code in a host which has its source which is external. Its main intention is to gain resources in host which is not legitimate in normal case. There is a fancy expansion for VIRUS i.e Vital Information Retrieval Under Siege. Mark Ludwig in his book titled “The Gaint Black Book of Computer Virus” expresses that all the virus can be broadly classified into three types. They are: i)Over writing ii)Companion iii)Parasitic. All the malicious code will exhibit either or all of the above mentioned basic behavior. To play with code ,especially virus it is really essential to get closer to the machine. In the sense, it is necessary to learn the assembly language(May be 8086). And this is it for intro! Hope that I would find time to post further details in the upcoming posts.