These are harmless memory resident parasitic viruses. They hook INT 21h and write themselves at the end of COM- and EXE-files that are executed, and they infect the files only if the ScrollLock key is pressed. On installation they hit COMMAND.COM file. They contain the internal text string:
COMSPEC=
# Bengal Tiger, v3p0x #
# By Trurl, the great constructor, 1993#
# Buenos Aires, Argentina #
Trurl
