A popular and dreaded type of trojan back in the bad old days of DOS, BBSes, cracking. Assuming ANSI.SYS was loaded, particular escape codes, when displayed to the screen, could remap the keyboard to perform destructive macros when a key is pressed. These could be embedded in text files or even in .ZIP comments that were displayed when an archive was uncompressed. Obviously, as with most trojans, these never lasted long because of their obvious destructive nature. Additionally, safe versions of ANSI.SYS and pkZIP were distributed. More to the point, the usage of ANSI.SYS, and DOS itself made the entire problem moot. Much like "phone phreaking," you still see outdated references to ANSI bombs on 37337 "underground" sites today.