mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 20:35:25 +00:00
331 lines
6.9 KiB
NASM
331 lines
6.9 KiB
NASM
|
; Date : 27-1-1989
|
|||
|
|
; Ver : 1.04
|
|||
|
|
; Program : Kill the Brain Virus
|
|||
|
|
Cseg Segment Para Public 'MyCode'
|
|||
|
|
Assume cs:Cseg,ds:Cseg
|
|||
|
|
Org 100h
|
|||
|
|
Start: Mov dx,offset CRight ;print copyright notice
|
|||
|
|
Call DispStr
|
|||
|
|
Mov ah,19h ;get current drive
|
|||
|
|
Int 21h
|
|||
|
|
Mov Drive,al ;save it
|
|||
|
|
Call GetDrive ;Get drive if possible
|
|||
|
|
Jc Exit
|
|||
|
|
Call ChVirus ;virus present?
|
|||
|
|
Jc Exit ;exit if not
|
|||
|
|
Call FindBoot ;Find correct boot sector
|
|||
|
|
Mov dx,offset VirusKill
|
|||
|
|
Call DispStr
|
|||
|
|
Call ReadFats ;Read the FAT tables
|
|||
|
|
Jc Exit
|
|||
|
|
Call CheckBad
|
|||
|
|
Exit: Mov ax,4C00h
|
|||
|
|
Int 21h
|
|||
|
|
FindBoot Proc
|
|||
|
|
Mov dl,[si+6]
|
|||
|
|
Mov ax,18 ;9 sectors/track * 2 sides
|
|||
|
|
Mov cl,[si+8]
|
|||
|
|
Mul cl
|
|||
|
|
Or dl,dl
|
|||
|
|
Jz Fb1
|
|||
|
|
Add ax,10 ;Move to the next side
|
|||
|
|
Fb1: Mov dx,ax ;read this sector
|
|||
|
|
Mov cx,1 ;Read one sector
|
|||
|
|
Mov bx,offset PrgEnd ;Read it here
|
|||
|
|
Mov al,Drive ;Get drive number
|
|||
|
|
Int 25h ;Read interrupt
|
|||
|
|
Jnc Fb2
|
|||
|
|
Add sp,2
|
|||
|
|
Mov dx,offset MesOh1
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
Fb2: Add sp,2
|
|||
|
|
Xor dx,dx ;Write at boot
|
|||
|
|
Mov cx,1 ;Write one sector
|
|||
|
|
Mov bx,offset PrgEnd ;Write from here
|
|||
|
|
Mov al,Drive ;Get drive number
|
|||
|
|
Int 26h ;Write interrupt
|
|||
|
|
Jnc Fb3
|
|||
|
|
Add sp,2
|
|||
|
|
Mov dx,offset MesOh2 ;Print message
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
Fb3: Add sp,2
|
|||
|
|
Clc
|
|||
|
|
Ret
|
|||
|
|
FindBoot Endp
|
|||
|
|
PointTo Proc
|
|||
|
|
Push bx
|
|||
|
|
Mov dx,ax
|
|||
|
|
Add ax,ax
|
|||
|
|
Add ax,dx
|
|||
|
|
Mov dx,ax
|
|||
|
|
Shr ax,1 ;Cluster * 1.5
|
|||
|
|
Mov bx,offset PrgEnd
|
|||
|
|
Add bx,ax
|
|||
|
|
Mov ax,ds:[bx] ;Get entry
|
|||
|
|
Test dx,1
|
|||
|
|
Jnz Point1
|
|||
|
|
And ax,0FFFh
|
|||
|
|
Jmp short Point0
|
|||
|
|
Point1: Shr ax,1
|
|||
|
|
Shr ax,1
|
|||
|
|
Shr ax,1
|
|||
|
|
Shr ax,1
|
|||
|
|
Point0: Pop bx
|
|||
|
|
Ret
|
|||
|
|
PointTo Endp
|
|||
|
|
ReadFats Proc
|
|||
|
|
Mov bx,offset PrgEnd
|
|||
|
|
Mov al,Drive
|
|||
|
|
Mov cx,4 ;read FAT1 and FAT2
|
|||
|
|
Mov dx,1 ;FAT sectors
|
|||
|
|
Int 25h ;Read FAT tables
|
|||
|
|
Jnc Rf1
|
|||
|
|
Add sp,2
|
|||
|
|
Mov dx,offset FatError
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
Rf1: Add sp,2
|
|||
|
|
Clc
|
|||
|
|
Ret
|
|||
|
|
ReadFats Endp
|
|||
|
|
|
|||
|
|
CheckBad Proc
|
|||
|
|
Call FindBad ;Find real boot sector
|
|||
|
|
Call WriteFats
|
|||
|
|
Exit1: Ret
|
|||
|
|
CheckBad Endp
|
|||
|
|
FindBad Proc
|
|||
|
|
Mov cx,354 ;Check 354 clusters
|
|||
|
|
Mov ax,2 ;start with cluster 2
|
|||
|
|
Mov bx,ax
|
|||
|
|
FM: Call PointTo ;Find where it points
|
|||
|
|
Cmp ax,0FF7h ;Is it bad?
|
|||
|
|
Jz ChkBd ;Check if realy bad
|
|||
|
|
FindMore1: Inc bx
|
|||
|
|
Mov ax,bx
|
|||
|
|
Loop FM
|
|||
|
|
Ret
|
|||
|
|
ChkBd: Push ax
|
|||
|
|
Call CheckCluster ;bx=cluster number, try to read
|
|||
|
|
Pop ax
|
|||
|
|
Jmp short FindMore1
|
|||
|
|
FindBad Endp
|
|||
|
|
WriteFats Proc
|
|||
|
|
Mov bx,offset PrgEnd
|
|||
|
|
Mov al,Drive
|
|||
|
|
Mov cx,4 ;FAT1 and FAT2
|
|||
|
|
Mov dx,1 ;Start of FAT sectors
|
|||
|
|
Int 26h ;Write FAT tables
|
|||
|
|
Jnc Wf1 ;Jump if not fail
|
|||
|
|
Add sp,2
|
|||
|
|
Mov dx,offset MesOh3 ;Write error
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
Wf1: Add sp,2
|
|||
|
|
Clc
|
|||
|
|
Ret
|
|||
|
|
WriteFats Endp
|
|||
|
|
CheckCluster Proc
|
|||
|
|
Push bx
|
|||
|
|
Push cx
|
|||
|
|
Sub bx,2
|
|||
|
|
Sal bx,1
|
|||
|
|
Add bx,12 ;bx=sector number
|
|||
|
|
Mov dx,bx ;sector
|
|||
|
|
Mov cx,2 ;2 sectors
|
|||
|
|
Mov bx,offset PrgEnd+205
|
|||
|
|
Mov al,Drive
|
|||
|
|
Int 25h ;Read sectors
|
|||
|
|
Jnc QRc1
|
|||
|
|
Add sp,2
|
|||
|
|
Mov al,2 ;err 2=try more
|
|||
|
|
Pop cx
|
|||
|
|
Pop bx
|
|||
|
|
Ret
|
|||
|
|
QRc1: Add sp,2
|
|||
|
|
Pop cx
|
|||
|
|
Pop bx ;Mark cluster bx as not bad
|
|||
|
|
Mov ax,bx
|
|||
|
|
Push bx
|
|||
|
|
Mov dx,ax
|
|||
|
|
Add ax,ax
|
|||
|
|
Add ax,dx
|
|||
|
|
Mov dx,ax
|
|||
|
|
Shr ax,1 ;Cluster * 1.5
|
|||
|
|
Mov bx,offset PrgEnd
|
|||
|
|
Add bx,ax
|
|||
|
|
Mov ax,ds:[bx] ;Get entry
|
|||
|
|
Test dx,1
|
|||
|
|
Jnz QPo1
|
|||
|
|
And ax,0F000h
|
|||
|
|
Jmp short QPo2
|
|||
|
|
QPo1: And ax,000Fh
|
|||
|
|
QPo2: Mov ds:[bx],ax ;Write entry to FAT1
|
|||
|
|
Mov ds:[bx+1024],ax ;Write entry to FAT2
|
|||
|
|
Pop bx
|
|||
|
|
Ret
|
|||
|
|
CheckCluster Endp
|
|||
|
|
|
|||
|
|
ChVirus Proc
|
|||
|
|
Call ReadBoot ;Read the boot sector
|
|||
|
|
Jnc ChVirus1
|
|||
|
|
Ret
|
|||
|
|
ChVirus1: Mov si,offset PrgEnd
|
|||
|
|
Mov dx,offset MesBad ;Assume bad news
|
|||
|
|
Cmp word ptr [si+4],1234h
|
|||
|
|
Jz InThere
|
|||
|
|
Mov dx,offset MesGood ;Assume all OK
|
|||
|
|
Mov di,436 ;Vector of interrupt 13h
|
|||
|
|
Push es
|
|||
|
|
Xor ax,ax
|
|||
|
|
Mov es,ax
|
|||
|
|
Mov ax,es:[di+2] ;get segment of the interrupt
|
|||
|
|
Pop es
|
|||
|
|
Cmp ax,0C800h
|
|||
|
|
Jb InThere
|
|||
|
|
Mov dx,offset MesBad1 ;active now!
|
|||
|
|
Call DispStr
|
|||
|
|
Mov bx,offset PrgEnd
|
|||
|
|
Mov ah,2 ;Read
|
|||
|
|
Mov al,1 ;1 sector
|
|||
|
|
Mov dl,Drive
|
|||
|
|
Xor dh,dh ;head number
|
|||
|
|
Xor ch,ch ;track number
|
|||
|
|
Mov cl,1 ;sector 1
|
|||
|
|
Int 6Dh ;Virus uses interrupt 6Dh
|
|||
|
|
Mov si,offset PrgEnd
|
|||
|
|
Mov dx,offset MesBad
|
|||
|
|
Cmp word ptr [si+4],1234h
|
|||
|
|
Jz InThere1
|
|||
|
|
Mov dx,offset MesGood
|
|||
|
|
Call DispStr
|
|||
|
|
Stc ;No need to do more.
|
|||
|
|
Ret
|
|||
|
|
InThere: Call DispStr
|
|||
|
|
Clc ;Do more
|
|||
|
|
Ret
|
|||
|
|
InThere1: Call DispStr ;write bad news
|
|||
|
|
Mov dx,offset MesBad2 ;No lasting effect
|
|||
|
|
Jmp short InThere
|
|||
|
|
ChVirus Endp
|
|||
|
|
ReadBoot Proc
|
|||
|
|
Mov bx,offset PrgEnd ;Put it here
|
|||
|
|
Mov al,Drive ;Drive to use
|
|||
|
|
Mov cx,1 ;One sector
|
|||
|
|
Xor dx,dx ;Boot sector
|
|||
|
|
Int 25h ;Read it
|
|||
|
|
Jnc P0
|
|||
|
|
Add sp,2
|
|||
|
|
Mov dx,offset MesBoot
|
|||
|
|
Cmp ah,80h ;Time-out?
|
|||
|
|
Jz P1
|
|||
|
|
Mov dx,offset MesBoot1
|
|||
|
|
P1: Call DispStr
|
|||
|
|
Stc ;Error
|
|||
|
|
Ret ;Go
|
|||
|
|
P0: Add sp,2
|
|||
|
|
Clc ;No error
|
|||
|
|
Ret ;Go
|
|||
|
|
ReadBoot Endp
|
|||
|
|
GetDrive Proc
|
|||
|
|
Mov si,80h
|
|||
|
|
Mov cl,[si] ;Get length of command tail
|
|||
|
|
Xor ch,ch
|
|||
|
|
Or cx,cx
|
|||
|
|
Jnz Lab1
|
|||
|
|
Cmp byte ptr Drive,2
|
|||
|
|
Jae DriveError1
|
|||
|
|
Clc
|
|||
|
|
Ret
|
|||
|
|
Lab1: Add si,cx
|
|||
|
|
Inc si
|
|||
|
|
Mov byte ptr [si],0 ;Command ends with 0
|
|||
|
|
Mov si,81h
|
|||
|
|
Cld
|
|||
|
|
SpOut: Lodsb
|
|||
|
|
Cmp al,32
|
|||
|
|
Jz SpOut ;Skip blanks
|
|||
|
|
Or al,al
|
|||
|
|
Jnz Stan1
|
|||
|
|
Ret
|
|||
|
|
|
|||
|
|
Stan1: Lodsb
|
|||
|
|
Or al,al
|
|||
|
|
Jnz Check1
|
|||
|
|
Ret
|
|||
|
|
Check1: Cmp al,':'
|
|||
|
|
Jnz Stan1
|
|||
|
|
Cmp si,84h
|
|||
|
|
DriveCheck: Jb DriveError
|
|||
|
|
Mov al,[si-2]
|
|||
|
|
And al,223 ;Convert to upper case
|
|||
|
|
Cmp al,'A'
|
|||
|
|
Jb DriveError1
|
|||
|
|
Cmp al,'B'
|
|||
|
|
Ja DriveError1
|
|||
|
|
Sub al,65 ;Convert drive to 0 or 1
|
|||
|
|
Mov Drive,al
|
|||
|
|
Clc
|
|||
|
|
Ret
|
|||
|
|
DriveError: Mov dx,offset Err8 ;Drive expected
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
DriveError1: Mov dx,offset Err9 ;Invalid drive
|
|||
|
|
Call DispStr
|
|||
|
|
Stc
|
|||
|
|
Ret
|
|||
|
|
GetDrive Endp
|
|||
|
|
DispStr Proc
|
|||
|
|
Mov ah,9
|
|||
|
|
Int 21h
|
|||
|
|
Ret
|
|||
|
|
DispStr Endp
|
|||
|
|
|
|||
|
|
CRight db 13,10
|
|||
|
|
db 'Kill the <Brain> virus Ver 1.04, 27-1-1989',13,10
|
|||
|
|
db '(C) Fragakis Stelios 1988,1989',13,10,13,10,'$'
|
|||
|
|
|
|||
|
|
|
|||
|
|
Err8 db 'Error 8 : Drive expected.$'
|
|||
|
|
Err9 db 'Error 9 : Invalid drive specified. Must be A or B.$'
|
|||
|
|
MesBoot db 13,10
|
|||
|
|
db 'Program execution aborted. Door open?',13,10,'$'
|
|||
|
|
MesBoot1 db 13,10
|
|||
|
|
db 'I can not read the boot sector.',13,10
|
|||
|
|
db 'Disk can not contain the virus <Brain>.',13,10,'$'
|
|||
|
|
FatError db 13,10
|
|||
|
|
db 'Sorry, I can not read the FAT tables.',13,10
|
|||
|
|
db 'FAT corrections not written to disk.',13,10,'$'
|
|||
|
|
VirusKill db 'Virus <Brain> was successfully killed.',13,10,'$'
|
|||
|
|
MesOh1 db 'DISK ERROR : I can not read the correct boot sector.'
|
|||
|
|
db 13,10,'$'
|
|||
|
|
MesOh2 db 'Failed to write correct boot sector in boot area.'
|
|||
|
|
db 13,10,'$'
|
|||
|
|
MesOh3 db 'Failed to write FAT tables. Corrections lost.'
|
|||
|
|
db 13,10,'$'
|
|||
|
|
MesGood db 'Good News : The disk is not <Brain> contaminated.'
|
|||
|
|
db 13,10,'$'
|
|||
|
|
MesBad db 'Bad News : The disk is <Brain> contaminated.'
|
|||
|
|
db 13,10,'$'
|
|||
|
|
|
|||
|
|
MesBad1 db '* WARNING *',13,10
|
|||
|
|
db 'Virus <Brain> is active right now !',13,10,'$'
|
|||
|
|
|
|||
|
|
MesBad2 db 13,10
|
|||
|
|
db 'Remove the disk after the virus is killed',13,10
|
|||
|
|
db 'to avoid the risk of contamination.',13,10,13,10,'$'
|
|||
|
|
|
|||
|
|
Count db 0 ;Count 0..58
|
|||
|
|
Drive db 0 ;Current drive
|
|||
|
|
|
|||
|
|
PrgEnd:
|
|||
|
|
Cseg Ends
|
|||
|
|
End Start
|
|||
|
|
|