Whenever that disk is loaded onto a new PC, the virus gets loaded too. When that PC connects to a network server, the virus connects too. Since most viruses remain hidden, most users have no idea they are passing around a deadly poison until it is too late. All computer programs are made up of thousands of lines of software code, the actual language that creates the program. The string of viral code hides itself amongst the normal code.
Most computer viruses fall into one of two categories - benign or malignant.
Although benign viruses quickly replicate, they tend not to corrupt data or attempt to do anything more devious than display annoying messages on the screen or frequently slow down your system. However, malignant viruses replicate very quickly with the intention of causing great harm to data stored on floppy disks or a computer's hard drive. Both benign and malignant viruses can be either boot sector viruses or file viruses. The boot sector is the portion of the disk reserved for the self-starting portion of a program. Boot sector viruses infect both the boot sector of a floppy disk as well as a computer hard drive.