In term computer virus was coined by , Fred Cohen in 1983 due to its ability to infect other programs like a normal virus . A year later Cohen released an official paper on virus in which he further described a virus as a that has the ability to make another program as a virus that can further infect other files .
There are certain types of files that are vulnerable to a virus .These are the files that can be executed and also some macro files like Microsoft word document fall into such category
Documents file formats like JPG, Adobe PDF's and other image formats cannot be used as a virus but can be affected by a virus though and get damaged .
A virus is spread through removable things like CD's ,Floppies ,USB Drives or can easily spread through internet ,Local area network in the form of files ,email attachments etc.
A computer virus is set of computer instructions that is written by somebody to intend damage. This instruction or tells the computer to perform some destructive tasks like deleting files infecting other files by replicating same code in those files or it can even get worse by crashing an Hard Disk. Some viruses have been known to do nothing more than put a smiley face or display some message on screen.But in all cases a virus is undesirable and needs to be checked by a good and updates Antivurs
