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2026-06-16 15:59:24 +00:00 · 2022-08-21 04:07:57 -05:00
parent 74dbd37f30
commit 4b9382ddbc
1392 changed files with 607600 additions and 607600 deletions
@@ -0,0 +1,171 @@
+;This is a disassembly of Thunderbyte's anti-viral partition code.
+;An org statement was not used because it appears that all offsets used 
+;herein are either relative or absolute, i.e. it just doesn't matter.
+;This should be compiled as a binary image file, it *WILL NOT* create 
+;an executable file. This code is exactly 512 bytes long and should be 
+;implanted into the hard drive at physical sector 1, cylinder 0, head 0
+;using the BIOS direct write to disk function. *DO NOT* use DOS write to 
+;disk functions or DEBUG because these functions can't access hidden sectors
+;and you'll probably just overwrite the disk drive.
+
+;have fun, folks!
+
+code_start:
+
+        cli                     ;no interrupts
+        xor     cx, cx
+        mov     ss, cx
+        mov     sp, 7c00h
+        mov     si, sp
+        sti
+        cld
+
+        mov     es, cx          ;cs already equals 0
+        mov     ds, cx
+
+        mov     di, 0600h       ;
+
+        mov     ch, 01          ;cx = 100h
+        repz    movsw           ;mov 200h bytes from 0000:7c00h to 0000:0600h
+                                ;to make room for boot sector
+
+jump_pt db      0e9h, 00, 8ah   ;this will act like far jmp to first_pt label
+                                ;i.e. 0000:061ah, wraps around segment
+first_pt:                       ;when execution continues, this will be offset
+                                ;061ah here
+        mov     si, 06ddh
+        call    routine_1
+        mov     si, 07eeh
+        call    routine_2
+        mov     bp, si
+        mov     si, 0733h
+        jb      second_pt
+        
+        mov     bx, sp          ;buffer at stack pointer (7c00h?)
+        mov     ax, 0201h       ;func 2, 1 sector - possibily boot sector?
+        int     13h             ;BIOS read sector
+
+        mov     si, 0725h
+second_pt:
+        jb      sixth_pt
+
+        mov     si, 745h
+        call    routine_1
+        call    routine_1
+                
+        mov     si, 7c40h
+        mov     cx, 01c0h
+loop_1:
+        xchg    ax, bx
+        shl     bx, 1
+        lodsb                   ;from 0000:7c40h
+        add     ax, bx
+        mov     ah, bh
+        test    ah, ah
+        jns     third_pt
+        xor     ax, 0a097h
+third_pt:
+        loop    loop_1
+
+        cmp     ax, 7805h
+        jnz     fourth_pt
+        mov     si, 0740h
+        call    routine_1
+
+        mov     si, 0762h
+        call    01cdh
+        mov     dx, [si + 0fc9fh]
+        cmp     dx, 27eh
+        jb      fourth_pt
+
+        mov     si, 740h
+        call    routine_1
+        mov     si, 774h
+        call    routine_1
+
+        les     ax, [004c]
+        mov     bx, es
+        mov     cl, 04
+        shr     ax, cl
+        add     ax, bx
+        inc     cx
+        inc     cx
+        shl     dx, cl
+        cmp     ax, dx
+        jnb     fifth_pt
+
+fourth_pt:
+        mov     si, 0787h
+        call    routine_1
+        int     16h
+        mov     si, 783h
+        or      al, 20h
+        cmp     al, 79h
+        jnz     seventh_pt
+
+fifth_pt:
+        call    routine_1
+        mov     si, bp
+        mov     dx, [si]
+        jmp     sp              ;control goes to boot sector
+
+sixth_pt:
+        call    routine_1
+        int     16h
+
+seventh_pt:
+        int     18h             ;rom BASIC!
+
+eighth_pt:
+        jmp     eighth_pt        ;infinite loop Lock Up!
+
+
+routine_2:
+        lea     di, [si - 30h]
+boot_chk:
+        cmp     byte ptr [si], 80h      ;looks like check for bootable parttn
+        jz      bootable
+        sub     si, 10h
+        cmp     si, di
+        jnb     boot_chk
+        ret
+bootable:
+        mov     dx, [si]
+        mov     cx, [si + 2]
+return_pt:
+        ret
+
+routine_1:
+        lodsb
+        cbw                             ;convert to word
+        test    ax, ax                  ;huh?
+        jz      return_pt               ;like ret to original caller      
+                        
+        mov     ah, 0eh
+        xor     bx, bx
+        push    si
+        int     10h
+        pop     si
+        jmp     routine_1
+
+code_end:
+
+        msg1    db      13, 10, "Thunderbyte anti-virus partition "
+                db      "v6.24 (C) 1993-94 Thunderbyte BV.", 13, 10, 10, 0
+        msg2    db      "Disk error!", 13, 10, 00
+        msg3    db      "No system!", 13, 10, 00
+        msg4    db      "OK!", 13, 10,"Checking ",0
+        msg5    db      "bootsector CRC -> ",0
+        msg6    db      "available RAM -> ",0
+        msg7    db      "INT 13h -> ",0
+        msg8    db      "OK!",13, 10, 10, 0
+        msg9    db      "Failed!", 13, 10, "System might be infected. Continue? (N/Y)", 07, 0
+
+        misc    db      0, 0, 0, 80h, 01h, 01, 0, 06, 0dh, 0feh, 0f8h
+                db      03eh, 0, 0, 0, 06h, 78h, 0dh, 0, 0, 0
+                db      10h     dup(0)
+                db      10h     dup(0)
+                db      0eh     dup(0)
+
+        id_sig  db      55h, 0aah
+