Malevolent software that spreads itself automatically by infesting other files on your PC. Software which attaches to other software. A boot virus inserts its code into the boot record or master boot record of a disk, so that when the machine boots from that disk, the virus code is executed. A file virus inserts its code into an executable file, so that when that file is executed, the virus is executed as well. A macro virus attaches itself to documents like Word or Excel.
