It's a overwriting DOS virus which infects COM programs by overwriting first 127 bytes (which makes all programs permamently damaged). It will infect only one COM program in current directory per execution. When all COM programs are infected in current directory, it will alter the system video characteristics so that any output sent to the system display will be scrolled diagonally down the screen until user reboots.
Why am I calling it Trivial instead of ZigZag? I want to stick to the KAV (Kaspersky AV) instead of messing various aliases (In this case, that would be "Virus.DOS.Trivial.127.c" for Kaspersky, "ZigZag" for ESET, while for AVG it would be "ZigZag.127.B", but do you really think I would use AVG aliases? Nope.). Of course, I might mention another aliases just in case for easier identification.
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Virus.DOS.Trivial or Trivial is a virus that runs on MS-DOS.