virus

File VirusesChapter 11. File Viruses1.1 IntroductionThis group contains viruses using the OS (a particular one or severalones) file system in one way or another to propagate. (Definitions taken fromAVP web site)The possibility of incorporating a file virus into virtually any executableof virtually any popular OS does exist. As of today there are known virusesinfecting all kinds of executables of standard DOS: batch command files(BAT), loadable drivers (SYS, including special purpose files IO.SYS and MS-DOS.SYS) and binary executables (EXE, COM). There also exist virusestargeting executables of other operating systems - Windows 3.x,Windows95/NT, OS/2, Macintosh, Unix, including the VxD drivers of Windows3.x and Windows95.There are also are viruses infecting files containing program sourcecode, libraries or object modules. Viruses that also save themselves in datafiles, but these happens either as a result of erratic behavior of the virus, orwhen the virus's aggressive routine is at work. Macro viruses also save theircode in databases - documents or spreadsheets - but these viruses are sopeculiar that they are put into separate group.According to the method of infecting files, viruses are divided into"overwriting", "parasitic", "companion" viruses, "link" viruses, worm virusesand viruses infecting object modules (OBJ), compiler libraries (LIB) andsource code.5