THE ART OF COMPUTER VIRUS RESEARCH AND DEFENSE [Electronic resources]

3.16. Host Size Dependency

To infect applications accurately, many computer viruses have limits on how small or how large the applications they infect can be. For instance, COM files on DOS cannot load if they are larger than a code segment. Consequently, most DOS viruses introduce limits to avoid infecting files that would grow past acceptable limits if the virus code were included in them.Chapter 6, "Basic Self-Protection Strategies") to avoid test files that computer virus researchers use.